# Are Your Spark Plugs Gapped Incorrectly?



## XtremeRevolution (Jan 19, 2012)

I'm creating this thread to increase exposure of what appears to be a very common issue (affecting 100% of Cruzes so far). This stemmed from the following thread:

http://www.cruzetalk.com/forum/27-fuel-economy/6468-spark-plug-gap-fe-1-4t.html

My original experiment was to increase spark plug gap over what they are gapped from the factory and test for measurable gains in fuel economy. What I didn't realize was that I had actually gapped them to the correct spec, and they were gapped much too small from the factory. 

AllData specifies a spark plug gap of *.033-.037* for the *1.4L Turbo* motor. Reports so far have come back with *.024, .025, .026, and .029* as measured spark plug gaps from the factory iridium plugs. These should have been pre-gapped from the distributor, but clearly weren't.

Coinneach checked his spark plug gap on his Cruze LS with the *1.8L N/A* motor and found a *.020* spark plug gap, which is absurd for a N/A motor and is smaller than he or I have ever seen before in any engine. He increased that to .035 and had the following to say when I asked if he noticed a difference:



> Like a whole new beast. It's not quite as zippy as the 1.4T in the Eco that I drove when I was shopping, but it's a *censored* of a lot snappier now.




I currently don't know what AllData specifies for the Cruze LS, but if someone can get that information into this thread, it would be of great benefit to everyone. Hopefully, someone will get a tutorial/video made soon. There are significant performance and fuel economy gains to be had by *correcting *the spark plug gaps on these cars.


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## silverram323 (Mar 16, 2012)

Thanks X, i seen the the other thread before, I will be checking both cars.
You have a link to were it calls for .33-.37 gap on 1.4L motor?

Sent from my DROID X2


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## XtremeRevolution (Jan 19, 2012)

Got this from a buddy of mine on w-body.com. Click to enlarge. 

ECO:


LS




What I want to know is why AllData specifies a smaller spark plug gap for the 1.8L than it does for the 1.4L Turbo. It's usually the other way around. 

That said, I can't see anything wrong with gapping the 1.8L motor bigger than the spec. There definitely won't be any danger of spark blowout with that motor running a .035 gap.


Edit: the images got screwed up for some reason. 

In any case, AllData and GM both call for .033-.037 on the 1.4L Turbo, and .028 on the 1.8L N/A motor. I would say everyone can safely run .035 regardless of motor.


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## 70AARCUDA (Nov 14, 2010)

...ah, but the "real" question should be: _"...what does *GM* specify the gap *should* be?"_


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## XtremeRevolution (Jan 19, 2012)

70AARCUDA said:


> ...ah, but the "real" question should be: _"...what does *GM* specify the gap *should* be?"_


Same thing. That has already been checked and verified in the thread I linked in the initial post, only they went a bit further and added another decimal point of value.


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## coinneach (Apr 10, 2012)

Cuda, the gap specs aren't the problem; it's that our cars are being delivered with incorrectly gapped plugs.


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## Beaker (Mar 21, 2012)

My question (and really everyone's should be) is are the plugs gapped wrong or is GMs listed spec wrong?


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## XtremeRevolution (Jan 19, 2012)

Beaker said:


> My question (and really everyone's should be) is are the plugs gapped wrong or is GMs listed spec wrong?


My guess is that since everyone's findings are all over the place and are nowhere near accurate that GM's and Alldata's listed specs are correct. Seriously, .020 on the 1.8L? That's laughable.


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## coinneach (Apr 10, 2012)

Beaker said:


> My question (and really everyone's should be) is are the plugs gapped wrong or is GMs listed spec wrong?


Considering the increase in economy and performance we've uniformly seen after regapping, I'd say the former.


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## iKermit (Dec 13, 2010)

How the ef do i do this, and where did i put my dad's spark plug ratchet thing.


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## XtremeRevolution (Jan 19, 2012)

iKermit said:


> How the ef do i do this, and where did i put my dad's spark plug ratchet thing.


You do this one step at a time, patiently and slowly. I believe it's the smaller of the common spark plug sockets to get it out. You'll also need a torx bit, but I don't remember what size it was. Don't adjust gap with one of those coin looking things; you'll need proper feeler gauges. You might otherwise damage the plug as it's an iridium tip. Once you get the engine cover off, the coil bar is right in the center with the two bolts that need removing, and you can wiggle it right out (again, patiently and slowly). Check inside the boots to make sure the springs didn't bind, and proceed to the spark plugs.


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## coinneach (Apr 10, 2012)

XtremeRevolution said:


> You do this one step at a time, patiently and slowly. I believe it's the smaller of the common spark plug sockets to get it out. You'll also need a torx bit, but I don't remember what size it was. Don't adjust gap with one of those coin looking things; you'll need proper feeler gauges. You might otherwise damage the plug as it's an iridium tip. Once you get the engine cover off, the coil bar is right in the center with the two bolts that need removing, and you can wiggle it right out (again, patiently and slowly). Check inside the boots to make sure the springs didn't bind, and proceed to the spark plugs.


It's the 5/8" spark plug socket and T-40 torx bit.


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## AkotaHsky (Feb 11, 2012)

XtremeRevolution said:


> You do this one step at a time, patiently and slowly. I believe it's the smaller of the common spark plug sockets to get it out. You'll also need a torx bit, but I don't remember what size it was. Don't adjust gap with one of those coin looking things; you'll need proper feeler gauges. You might otherwise damage the plug as it's an iridium tip. Once you get the engine cover off, the coil bar is right in the center with the two bolts that need removing, and you can wiggle it right out (again, patiently and slowly). Check inside the boots to make sure the springs didn't bind, and proceed to the spark plugs.


I've only just used a coin thing. What do you suggest we use for gapping them correctly..?


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## XtremeRevolution (Jan 19, 2012)

AkotaHsky said:


> I've only just used a coin thing. What do you suggest we use for gapping them correctly..?


Something that looks similar to this:


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## crzyfirefighter (Apr 19, 2012)

going to be doing this later today as soon as i get home from work


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## XtremeRevolution (Jan 19, 2012)

crzyfirefighter said:


> going to be doing this later today as soon as i get home from work


Please report back with what you find as far as the original gaps go.


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## AkotaHsky (Feb 11, 2012)

XtremeRevolution said:


> Please report back with what you find as far as the original gaps go.


How much does that cost

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## coinneach (Apr 10, 2012)

AkotaHsky said:


> How much does that cost
> 
> Sent from my PC36100 using AutoGuide.Com Free App


Adjusting the gap, assuming you have the tools, costs nothing but maybe 15 minutes of your time. The gap tool shouldn't cost more than $3 or so at Pep Boys, Autozone, etc.


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## AkotaHsky (Feb 11, 2012)

coinneach said:


> Adjusting the gap, assuming you have the tools, costs nothing but maybe 15 minutes of your time. The gap tool shouldn't cost more than $3 or so at Pep Boys, Autozone, etc.


The cost of the tool is my question. Thats the tool linked above? Or just a coin gapper? It looks like itd be more than $3.

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## XtremeRevolution (Jan 19, 2012)

AkotaHsky said:


> The cost of the tool is my question. Thats the tool linked above? Or just a coin gapper? It looks like itd be more than $3.
> 
> Sent from my PC36100 using AutoGuide.Com Free App


Coin gappers aren't recommended with iridium plugs. You can try it, but there's a chance you could break the tip.

Not sure how much the other tools are. 

Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


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## Vetterin (Mar 27, 2011)

coinneach said:


> It's the 5/8" spark plug socket and T-40 torx bit.


Actually it's a T-27 torx (same size that you use for your rear brake drum screw removal).
Anyway, I just pulled my plugs 10 minutes ago and sure enough, 3 were @ .024 and 1 @ .025. I regapped to .034 and can't wait for my drive to work tomorrow. The entire job took 15 minutes. Man do I love working on this engine. For those that are going to check theirs DO make sure you check the springs inside the spark plug boot as I found 2 that were kinked to the side and I don't think it was caused by me but installed that way.


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## sciphi (Aug 26, 2011)

Vetterin said:


> Actually it's a T-27 torx (same size that you use for your rear brake drum screw removal).
> Anyway, I just pulled my plugs 10 minutes ago and sure enough, 3 were @ .024 and 1 @ .025. I regapped to .034 and can't wait for my drive to work tomorrow. The entire job took 15 minutes. Man do I love working on this engine. For those that are going to check theirs DO make sure you check the springs inside the spark plug boot as I found 2 that were kinked to the side and I don't think it was caused by me but installed that way.


You sure you didn't do my engine? That's exactly what I found on mine. I regapped to a hair over 0.030". Good use for a traditional feeler gauge, and practice for the upcoming valve adjustment on our Honda.


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## XtremeRevolution (Jan 19, 2012)

sciphi said:


> You sure you didn't do my engine? That's exactly what I found on mine. I regapped to a hair over 0.030". Good use for a traditional feeler gauge, and practice for the upcoming valve adjustment on our Honda.


Sounds like you should up those a bit to .035.  

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## evo77 (Sep 5, 2011)

AkotaHsky said:


> The cost of the tool is my question. Thats the tool linked above? Or just a coin gapper? It looks like itd be more than $3.
> 
> Sent from my PC36100 using AutoGuide.Com Free App


 http://www.autozone.com/autozone/ac...ByKeyWord=spark+plug+gapper&fromString=search


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## UR2NOZ (Mar 10, 2012)

Did this to mine yesterday. 1.4L Looks like all were right about .25-.26. I took them all up to .35. So far I wasn't in shock and awe after the adjustment but I didn't expect to be either. Car runs smooth fuel mileage seems the same based on my normal 80miles round trip to work each day.


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## XtremeRevolution (Jan 19, 2012)

UR2NOZ said:


> Did this to mine yesterday. 1.4L Looks like all were right about .25-.26. I took them all up to .35. So far I wasn't in shock and awe after the adjustment but I didn't expect to be either. Car runs smooth fuel mileage seems the same based on my normal 80miles round trip to work each day.


Wait till you fill up at the pump after the tank is through. I'd expect a 1-2mpg boost.


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## bubby2411 (Sep 3, 2011)

going to check mine to see what they are, if they are at the .2 range i will be going to buy ngk spark plugs and putting new ones in my car! hopefully i can check it this weekend


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## XtremeRevolution (Jan 19, 2012)

bubby2411 said:


> going to check mine to see what they are, if they are at the .2 range i will be going to buy ngk spark plugs and putting new ones in my car! hopefully i can check it this weekend


No need for NGK spark plugs. The ones in the Cruze are excellent and are Iridium plugs as well. You'd see zero gains going with an NGK plug over what's in there already, but you'd see a hole in your wallet instead.


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## crzyfirefighter (Apr 19, 2012)

ok just got doing this to my cruze with the 1.4l turbo... man glade i did... one was gaped at not even .19 and the others not even close to .25... gaped them all at about .36... went and fuelled up.. will report back later in the week what my mpg are.. i've been getting about 25 to 27 mpg on a full tank....again glad i did this.. thanks for the heads up


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## XtremeRevolution (Jan 19, 2012)

crzyfirefighter said:


> ok just got doing this to my cruze with the 1.4l turbo... man glade i did... one was gaped at not even .19 and the others not even close to .25... gaped them all at about .36... went and fuelled up.. will report back later in the week what my mpg are.. i've been getting about 25 to 27 mpg on a full tank....again glad i did this.. thanks for the heads up


.19!!! Wow. It's disturbing to find that these are gapped so far off what they should be, and so inconsistently at that! 

Did you notice any difference in how the car drove?


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## UR2NOZ (Mar 10, 2012)

XtremeRevolution said:


> No need for NGK spark plugs. The ones in the Cruze are excellent and are Iridium plugs as well. You'd see zero gains going with an NGK plug over what's in there already, but you'd see a hole in your wallet instead.


Wait....mine has factory NGK plugs installed. Do they not all come with NGK anyhow? I am confused.


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## XtremeRevolution (Jan 19, 2012)

UR2NOZ said:


> Wait....mine has factory NGK plugs installed. Do they not all come with NGK anyhow? I am confused.


Are they NGKs from the factory? I never bothered to actually check what brand they were. If they are, even better!


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## UR2NOZ (Mar 10, 2012)

XtremeRevolution said:


> Are they NGKs from the factory? I never bothered to actually check what brand they were. If they are, even better!


Yes Sir, says right on the plugs. I to was surprised.


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## crzyfirefighter (Apr 19, 2012)

XtremeRevolution said:


> .19!!! Wow. It's disturbing to find that these are gapped so far off what they should be, and so inconsistently at that!
> 
> Did you notice any difference in how the car drove?


seemed a bit peppier.. didn't really have to drive to far for gas.. so i will pay attention tomorrow on the way to work.. and yes it was quite a difference in the gap... plus all the springs were wedged off to the side...


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## OnlyTaurus (Mar 20, 2012)

Here.. if you guys did not know.

GM's specified gaps(directly from SI):

1.4L - 0.0335–0.0374 in
1.8L - 0.028 in


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## XtremeRevolution (Jan 19, 2012)

OnlyTaurus said:


> Here.. if you guys did not know.
> 
> GM's specified gaps(directly from SI):
> 
> ...


Yep, we've confirmed this. Thanks for confirming it again (being honest, no sarcasm). What confuses me is why they recommended such a small gap for the N/A motor and a larger gap for the Turbo motor, lol. Coineeach seems to be loving his .035 gap on his LS though.


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## UR2NOZ (Mar 10, 2012)

crzyfirefighter said:


> seemed a bit peppier.. didn't really have to drive to far for gas.. so i will pay attention tomorrow on the way to work.. and yes it was quite a difference in the gap... plus all the springs were wedged off to the side...


Springs were not wedged originally. When you unseated the coils from the plugs they do that FYI.


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## OnlyTaurus (Mar 20, 2012)

XtremeRevolution said:


> Yep, we've confirmed this. Thanks for confirming it again (being honest, no sarcasm). What confuses me is why they recommended such a small gap for the N/A motor and a larger gap for the Turbo motor, lol. Coineeach seems to be loving his .035 gap on his LS though.


I would assume the larger gap for more volume and dense air from turbo. Smaller for just atmospheric pressure. Like you said preivously, larger gap ensures all the mixture is burned.


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## crzyfirefighter (Apr 19, 2012)

UR2NOZ said:


> Springs were not wedged originally. When you unseated the coils from the plugs they do that FYI.


my bad.. first time doing anything with this car... only had it for about 3 weeks now


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## XtremeRevolution (Jan 19, 2012)

OnlyTaurus said:


> I would assume the larger gap for more volume and dense air from turbo. Smaller for just atmospheric pressure. Like you said preivously, larger gap ensures all the mixture is burned.


Right, it's just that historically, they've used smaller gaps on forced induction motors to prevent spark blowout. The spark plug gap for my N/A 95 Regal was .060 to give people a comparison.


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## Higgs Boson (Mar 7, 2012)

I gapped mine to 35 and see no difference in mileage or power over 600 miles even though I really wanted to. plugs were gapped at 25 stock. be careful gapping these plugs, you can bend or break the electrode easily. use pliers to pull the ground strap up and then bend them down on the ground. a normal gap tool will ruin your plugs.


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## XtremeRevolution (Jan 19, 2012)

Higgs Boson said:


> I gapped mine to 35 and see no difference in mileage or power over 600 miles even though I really wanted to. plugs were gapped at 25 stock. be careful gapping these plugs, you can bend or break the electrode easily. use pliers to pull the ground strap up and then bend them down on the ground. a normal gap tool will ruin your plugs.


I went over this in a bit of detail a few posts (or pages) back, regarding which tools to use and why. A coin-type tool is not how people should be gapping iridium tipped plugs. Feeler gauges need to be used or a specific spark plug gapping tool. 

Try putting your gaps back to .025 and see if you see a difference again. I know I felt a difference for sure, but it was mostly at lower RPMs, which the auto transmission won't really let you get into a whole lot.


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## OnlyTaurus (Mar 20, 2012)

Technology has come a long way my friend. They still use .060 now, and quite frequently at that. I believe most of GM's V6 and V8's use that gap.


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## coinneach (Apr 10, 2012)

Vetterin said:


> Actually it's a T-27 torx (same size that you use for your rear brake drum screw removal).


Beg to differ. You can certainly use a 27, but 40 is more snug and doesn't slop around like a 27 or 30. Yes, even on the drums.


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## XtremeRevolution (Jan 19, 2012)

coinneach said:


> Beg to differ. You can certainly use a 27, but 40 is more snug and doesn't slop around like a 27 or 30. Yes, even on the drums.


Agreed here. I ended up using my T27 a few minutes ago, but it wasn't as tight as I like it to be. Fortunately, these aren't on there very tight from the factory and can be removed even with a bit that goes into the end of a screwdriver. 

I gapped my plugs to .040 and went out for a drive, scanning for KR and misfire events with Torque. Not a single issue. I'll be scanning the whole way to work tomorrow. I think I'm content at .040. That's only .003 larger than the GM/Alldata spec. Engine is smooth across the powerband and feels great.

I'll report my fuel economy when I fill up this week.


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## Chevy Customer Care (Oct 29, 2011)

I would like to look into this for anyone who has confirmed that their spark plugs are gaped incorrectly. Please send me a PM with your name, address, phone number, VIN, current mileage and the name of your dealership. I look forward to hearing back from and assisting anyone with this issue. If you have any other questions please feel free to contact me as well.
Thank you,
Stacy Chevrolet Customer Service


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## H3LLON3ARTH (Dec 16, 2011)

Chevy Customer Service said:


> I would like to look into this for anyone who has confirmed that their spark plugs are gaped incorrectly. Please send me a PM with your name, address, phone number, VIN, current mileage and the name of your dealership. I look forward to hearing back from and assisting anyone with this issue. If you have any other questions please feel free to contact me as well.
> Thank you,
> Stacy Chevrolet Customer Service


What will you be able to do about this problem.

Sent from my Droid


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## silverram323 (Mar 16, 2012)

Both of my cruzes were at .024
They are now at .035

Sent from my DROID X2


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## rbtec (Feb 3, 2012)

Chevy Customer Service said:


> I would like to look into this for anyone who has confirmed that their spark plugs are gaped incorrectly. Please send me a PM with your name, address, phone number, VIN, current mileage and the name of your dealership. I look forward to hearing back from and assisting anyone with this issue. If you have any other questions please feel free to contact me as well.
> Thank you,
> Stacy Chevrolet Customer Service


Stacy,
Can you look into the issues with coolant leaks/smell? This seems to be a major issue and many people would like to know what GM is doing about it. I'm sure that lots of people, including myself, feel like the Cruze is a ticking time bomb with all these issues people are having. 


Sent from my Autoguide iPhone app


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## Vetterin (Mar 27, 2011)

coinneach said:


> Beg to differ. You can certainly use a 27, but 40 is more snug and doesn't slop around like a 27 or 30. Yes, even on the drums.


My bad! You are right in that T-40 IS the correct size for the M6 X75 bolt.
As for my ride to work today it did feel like the car had a smoother low end pick-up but couldn't tell if the gas mileage was affected as the expressways were all fk'd up this morning.


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## XtremeRevolution (Jan 19, 2012)

H3LLON3ARTH said:


> What will you be able to do about this problem.
> 
> Sent from my Droid


Write a case for it, file a complaint with engineering, find you a dealer and set up an appointment for you to take it in and have the dealer do it. Maybe with enough reports and complaints, GM will wake up and realize they're not gapping the plugs correctly when they're delivering the cars to the dealers. 



Vetterin said:


> My bad! You are right in that T-40 IS the correct size for the M6 X75 bolt.
> As for my ride to work today it did feel like the car had a smoother low end pick-up but couldn't tell if the gas mileage was affected as the expressways were all fk'd up this morning.


I also can't tell if gas mileage improved yet. If it does, it will probably be in the range of 1-2mpg. I did also notice a smoother low end acceleration.


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## XtremeRevolution (Jan 19, 2012)

I had to copy this over here as well:



Beachernaut said:


> Got bored during my lunch break and decided to check mine. All 4 varied between .024 and .026. I set them at .035. It literally took 10 minutes.
> 
> On the way back to work I did notice the low RPM hesitation is gone.


If anyone reports hesitation at lower RPMs, looks like we have a solution!


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## sciphi (Aug 26, 2011)

I noticed the car ran better at low RPM's. I think the Eco MT's and other MT-car folks are noticing the most benefit since the AT will shift well before the RPM's involved. The improvement was noticed the most between 1000 and 1500 RPM's. I spend a lot of time between those two RPM ranges.


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## Starks8 (Jul 20, 2011)

Is this correction doing much for those with Cruzes with AT?


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## XtremeRevolution (Jan 19, 2012)

Starks8 said:


> Is this correction doing much for those with Cruzes with AT?


There should be a definite increase in fuel economy. It may not be much (1-2mpg), but it's something nonetheless. AT Cruzes may not notice it as much, but there will also be a slight increase in performance.


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## parish8 (Mar 11, 2012)

XtremeRevolution said:


> There should be a definite increase in fuel economy. It may not be much (1-2mpg), but it's something nonetheless. AT Cruzes may not notice it as much, but there will also be a slight increase in performance.


i see no reason to expect a mileage gain and no reason to predict a 1-2 gain either but i am certainly hoping that there is.

this is one of those cases where i think your talking out your ass but hope your right


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## WHITECO (Mar 31, 2011)

just re-gapped mine last night....Did notice an improvement for sure...Seems like a good thing to me!!


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## parish8 (Mar 11, 2012)

WHITECO said:


> just re-gapped mine last night....Did notice an improvement for sure...Seems like a good thing to me!!


i dont trust my butt meter at all but there are so many people here reporting an improvement in low rpm driveability i am starting to believe.... cant wait for the mileage reports to come in.


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## XtremeRevolution (Jan 19, 2012)

parish8 said:


> i see no reason to expect a mileage gain and no reason to predict a 1-2 gain either but i am certainly hoping that there is.
> 
> this is one of those cases where i think your talking out your ass but hope your right


As a result of these bad spark plug gaps, we're getting:

1. less than optimal fuel burn
2. hesitation at low rpms

As a result of correcting the gap, the car is:

1. a whole new animal (coinneach)
2. getting much better low end power delivery (everyone with a manual transmission)
3. running smoother throughout the powerband

The moment you start gaining power and not using more fuel to gain that power, you are gaining efficiency, which means you can use less fuel to go just as far, thus increasing fuel economy. The question to be determined is not whether or not there will be a gain, but how much that gain will be. 

1-2mpg is merely my speculation. I would be talking out of my ass if I guaranteed a 1-2mpg gain.


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## WHITECO (Mar 31, 2011)

parish8 said:


> i dont trust my butt meter at all but there are so many people here reporting an improvement in low rpm driveability i am starting to believe.... cant wait for the mileage reports to come in.


I would think that with a bit more power in the low rpm's that it should help with the fuel mileage...I guess we will see....I have 20,000 miles on mine and man the plugs looked really good....a nice clean burn on them....although the gaps were all over the place between the 4.....

I am thinking and this is just a guess that they gapped them smaller do to GM's no tune-up for 100,000 miles...as over time I would think they gaps would get wider so that they would end up at .035 after the 100,000 miles.....just a guess though


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## XtremeRevolution (Jan 19, 2012)

WHITECO said:


> I would think that with a bit more power in the low rpm's that it should help with the fuel mileage...I guess we will see....I have 20,000 miles on mine and man the plugs looked really good....a nice clean burn on them....although the gaps were all over the place between the 4.....
> 
> I am thinking and this is just a guess that they gapped them smaller do to GM's no tune-up for 100,000 miles...as over time I would think they gaps would get wider so that they would end up at .035 after the 100,000 miles.....just a guess though


I had that same suspicion, but I started doubting myself when I read people getting gap sizes that were all over the place. If they planned for the gap to get bigger, why would they have such a large variance? 

I don't know if we'll ever find out why they did this.


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## WHITECO (Mar 31, 2011)

XtremeRevolution said:


> I had that same suspicion, but I started doubting myself when I read people getting gap sizes that were all over the place. If they planned for the gap to get bigger, why would they have such a large variance?
> 
> I don't know if we'll ever find out why they did this.


When I used to drag race with Nitrous the gaps would widen over time as a result of the heat in the chamber...I had to check them ever couple times out as the gaps would widen and I would have to make sure it was smaller....I never wanted to have spark blowout with nitrous......

As for the Cruze...the 2 middle plugs were wider...I am guessing that those 2 cylinders run a bit hotter then the 2 outside one's...but the positive thing was that the engine is getting a nice clean burn which is a good sign just looking at the plugs real quick...I was quite surprised after 20,000 miles to see no black on the plugs


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## XtremeRevolution (Jan 19, 2012)

WHITECO said:


> When I used to drag race with Nitrous the gaps would widen over time as a result of the heat in the chamber...I had to check them ever couple times out as the gaps would widen and I would have to make sure it was smaller....I never wanted to have spark blowout with nitrous......
> 
> As for the Cruze...the 2 middle plugs were wider...I am guessing that those 2 cylinders run a bit hotter then the 2 outside one's...but the positive thing was that the engine is getting a nice clean burn which is a good sign just looking at the plugs real quick...I was quite surprised after 20,000 miles to see no black on the plugs


In your experience, did one type of plug last longer than another? Platinum, iridium, copper, etc?


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## parish8 (Mar 11, 2012)

a copper plug is going to wear. i dont think a platinum plug will wear at all, not measurable anyways but i have always been told not to run those with a turbo or nitrous. isn't iridium a little like platinum where there is a little disk of the material stuck to the electrode and ground strap?


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## WHITECO (Mar 31, 2011)

XtremeRevolution said:


> In your experience, did one type of plug last longer than another? Platinum, iridium, copper, etc?


I started out with copper cheap one's and they worked fine...I would change them every month or so...just in case....in the end I used NGK Iridium's and I used the same set for like a year....just re-gapping monthly

The Iridiums seemed to handle the heat better and of course I felt that they made better power...LOL


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## parish8 (Mar 11, 2012)

i found this on a spark plug site. makes me think that even after 100k miles it is unlikely that our plug gap would open up to the .035 spec's.

Iridium is a precious metal that is 6 times harder and 8 times stronger than platinum, it has a 1,200°(F) higher melting point than platinum and conducts electricity better. This makes it possible to create the finest wire center electrode ever. Prior till now, spark plug manufacturers have favored platinumfor their long life or performance spark plugs due to its high melting point. However platinum alone is no longer enough, ultra long life spark plugs and smaller center electrodes required harder and stronger precious metals. The strength, hardness and high melting point of iridium makes it very well suited for a fine wire plug and for ultra long life spark plugs. Though better, it’s not perfect, it is very expensive, and at higher temperatures it oxides, thus rendering pure iridium as an expensively poor choice for spark plug construction. However when blended with other precious metals such as Yttria, Rhodium or Platinum, you can enhance those metals advantages with the superior strength and hardness of Iridium. Almost all manufacturers have their own version of an iridium spark plug. DO NOT BE FOOLED, all iridium plugs are not the same. Iridium content varies, some of the lower priced iridium plugs have just enough iridium content so they can be marketed as iridium plugs. They likely will not perform or last as long as the plugs with a higher iridium content.


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## WHITECO (Mar 31, 2011)

parish8 said:


> i found this on a spark plug site. makes me think that even after 100k miles it is unlikely that our plug gap would open up to the .035 spec's.
> 
> Iridium is a precious metal that is 6 times harder and 8 times stronger than platinum, it has a 1,200°(F) higher melting point than platinum and conducts electricity better. This makes it possible to create the finest wire center electrode ever. Prior till now, spark plug manufacturers have favored platinumfor their long life or performance spark plugs due to its high melting point. However platinum alone is no longer enough, ultra long life spark plugs and smaller center electrodes required harder and stronger precious metals. The strength, hardness and high melting point of iridium makes it very well suited for a fine wire plug and for ultra long life spark plugs. Though better, it’s not perfect, it is very expensive, and at higher temperatures it oxides, thus rendering pure iridium as an expensively poor choice for spark plug construction. However when blended with other precious metals such as Yttria, Rhodium or Platinum, you can enhance those metals advantages with the superior strength and hardness of Iridium. Almost all manufacturers have their own version of an iridium spark plug. DO NOT BE FOOLED, all iridium plugs are not the same. Iridium content varies, some of the lower priced iridium plugs have just enough iridium content so they can be marketed as iridium plugs. They likely will not perform or last as long as the plugs with a higher iridium content.


This is why I just guess at things....


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## OnlyTaurus (Mar 20, 2012)

Pulled mine today and got these:

Cylinder 1- .023"
Cylinder 2- .023"
Cylinder 3- .025"
Cylinder 4- .025"

Adjusted all 4 to .035" with a feeler gauge. It feels like throttle response improved, but I could be imagining things. Im gonna fill the tank up tomorrow or saturday and test any MPG gains.


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## boats4life (May 28, 2011)

After speaking with Vince about this, we've come to the conclusion that it's safer in the higher boosted applications (if you're tuned) to keep the gap where GM put it from the factory. Ultimately, it's your car and if you want to gap your plugs further, that's up to you. I'm not touching mine...


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## XtremeRevolution (Jan 19, 2012)

boats4life said:


> After speaking with Vince about this, we've come to the conclusion that it's safer in the higher boosted applications (if you're tuned) to keep the gap where GM put it from the factory. Ultimately, it's your car and if you want to gap your plugs further, that's up to you. I'm not touching mine...


I'd like to hear the story behind this. What you said makes zero sense for the following reasons:

1. The gaps are all over the place, from .19 to .29 on the 1.4T. If GM knew exactly what they were doing when they gapped them from the factory, there would be at least some consistency, but there simply isn't. 
2. Both GM and AllData recommend .033-.037 for the 1.4T. If you waited 50,000 miles, then took your car in to get the spark plugs changed, take a guess as to what the dealer or shop will gap them to. 

Higher boosted applications? There are twin turbo LS1s running bigger gaps than we are.

How about the possibility that maybe someone will break into the 14s with the *correct *spark plug gap.


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## boats4life (May 28, 2011)

Just passing on what he said, I'm inclined to go with my tuners reccomendations. Each engine is different, which could explain why everyone has slightly different gaps. An LS1 runs a larger gap anyway, with or without turbos... Like I said, it's your car.


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## jblackburn (Apr 14, 2012)

Pulled mine just now. 

.020", 023", .025", .022". 

What the heck?

Much better torque down low now, and idle feels smoother. I now see how you guys can stand to shift at or below 2000 rpm. Lag from 2-3 shifting that low is still present but that gear is much taller. 

I'll have to see how it behaves in hot weather where my car seems to have the problem accelerating. But so far, with it 65 outside, it definitely feels "peppier". 


Sent from my Autoguide iPhone app


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## XtremeRevolution (Jan 19, 2012)

boats4life said:


> Just passing on what he said, I'm inclined to go with my tuners reccomendations. Each engine is different, which could explain why everyone has slightly different gaps. An LS1 runs a larger gap anyway, with or without turbos... Like I said, it's your car.


Don't get me wrong, I'll trust a tuner too, if he gives me a reason. Right now its incorrect gap and horrible inconsistency with variance even between spark plugs of the same engine, against GM's published spec. Will Vince change his tune when (not if) GM releases a TSB for this? 

Not one person has noticed any negative results yet, and why should they; they're finally running the gap the car was designed to, at least according to General Motors.

Not being rude or trying to be. My mind is simply blown that Vince would recommend an inconsistent and unpredictable gap. Boats, what are your plugs gapped to? 

It would be one thing if he said the higher boost with the Tune causes spark blowout at .035 and .030 or .025 is recommended for Trifecta owners. It's another thing entirely to say that we should leave them be even if we have a huge variance between our own spark plugs. 

I can't stress enough how much more smoothly my engine is running now that all of the plugs are gapped the same. If anything, at least pull them and make sure they all have the same gap, whether its .019, .020, .024, .025, .026, or .029 (all gaps reported by Cruze owners.) 

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## XtremeRevolution (Jan 19, 2012)

jblackburn said:


> Pulled mine just now.
> 
> .020", 023", .025", .022".
> 
> ...


This is what I'm talking about! Between .020 and .025 is a HUGE difference, and is a blatant and undeniable indicator that these spark plugs were never gapped before being installed. That step was skipped entirely. How anyone can be in favor of just leaving them alone is beyond me.

This whole scenario blows my mind on a number of levels.

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## blk88verde (Apr 30, 2011)

Yesterday, when Vince (of Trifecta) responded to my question regarding what spark plug gap for Trifecta tuned 1.4s, his response was .025 and further stated this is the gap that GM installs on the assembly line. I will be checking my plugs to make sure they are all at .025, since others are finding variances.


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## XtremeRevolution (Jan 19, 2012)

blk88verde said:


> Yesterday, when Vince (of Trifecta) responded to my question regarding what spark plug gap for Trifecta tuned 1.4s, his response was .025 and further stated this is the gap that GM installs on the assembly line. I will be checking my plugs to make sure they are all at .025, since others are finding variances.


Apparently that's not the case since these cars are coming off the assembly line with anywhere from .020 to .029. I don't think Vince actually knows what GM specified for these cars, and his notion that they should all be .025 is probably based on an observation of what they had when he measured them.

Why would GM and AllData specify a .033-.037 spark plug gap if they should actually be .025?

Not a single person who has checked theirs has reported consistency. Not one. I datalogged 50 miles today with varying degrees of throttle and RPM levels with a .040 gap and had zero misfires, blowout, or negative results. Believe me when I say I will post back immediately if I notice anything "off." Considering that I'm only .003" off from GM's spec, I doubt I will.


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## Skagit ECO (Sep 19, 2011)

*Mine were all 0.025"*

I regapped them to 0.035", drove 140 miles mostly I-5 and did not notice a difference in mileage (44) or seat of the pants performance. Here is a picture of the plugs aftter I regapped them. They are remarkably clean after 9,225 miles.


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## jblackburn (Apr 14, 2012)

> Yesterday, when Vince (of Trifecta) responded to my question regarding what spark plug gap for Trifecta tuned 1.4s, his response was .025 and further stated this is the gap that GM installs on the assembly line. I will be checking my plugs to make sure they are all at .025, since others are finding variances.


He may have tuned for it, but did GM originally?

My car felt like a dog (probably because of that .020" plug.


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## XtremeRevolution (Jan 19, 2012)

I can see where Vince might be able to make a case for a .025 spark plug gap if he experienced spark blowout with higher gaps, but otherwise, saying that we should keep them at .025 (when they simply aren't because of inconsistency) because that's the way they came out of the factory is not a very good reason IMO, especially given the fact that GM recommends a higher gap.

Whoever keeps in touch with him should ask him if he ever tried gapping the plugs to .033-.037 like GM actually specifies.


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## XtremeRevolution (Jan 19, 2012)

Skagit ECO said:


> I regapped them to 0.035", drove 140 miles mostly I-5 and did not notice a difference in mileage (44) or seat of the pants performance. Here is a picture of the plugs aftter I regapped them. They are remarkably clean after 9,225 miles.
> View attachment 5382


It may not be very noticeable with regard to fuel economy. That has yet to be determined and is still up in the air. You'll probably have to run an entire tank before you can measure a difference.


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## leeclark (Mar 25, 2012)

this is crazy! I'm pulling mine sunday and probably regapping them.


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## SlvrECObullet (Feb 21, 2012)

I'm gunna pull mine Friday when I get a chance and if I can find a Torx bit set... I'm gunna regap mine to a possible .0375.

As for the owners with Tunes. They Should Regap, Datalog a few tanks or so and send it to Vince, then the tune should change a bit, possibly for the better since our gaps have such big variences and they should be between .0335-.0375. Obviously someone at the plant is not doing there Job properly and QA checking the plugs before they get installed. Or its possible they QA check a handfull out of a TON... and saying GTG. 

Anyways Friday(today) I will be doing mine to .0375. I will report any findings.


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## SlvrECObullet (Feb 21, 2012)

Everyone who has to change there gap should or hopefully reporting it to GM through Stacy, Which I will be doing.


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## mcg75 (Mar 5, 2012)

Just to make sure, I logged into GM SI this morning and confirmed that the gap spec in this thread was correct and it is. I wonder if this would account for cars supposedly getting better milage with age? As the plug gets older, the gap starts to widen. More spark, more combustion and better fuel economy.


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## Higgs Boson (Mar 7, 2012)

It's not THAT crazy in that plug manufacturers say specifically to NOT gap iridium or platinum plugs, only copper. They come "pre-gapped" out of the box. So whoever puts the plugs in an the Cruze factory doesn't check, why would they?

The disconnect is between Chevy and NGK. The spec plug is out of spec. And I will bet if you did a careful test on the rest of your car you will find much more even further out of spec, lol. Calm down on the end of the world conspiracy stuff on your .010 spark plug gap.


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## sciphi (Aug 26, 2011)

Higgs Boson said:


> It's not THAT crazy in that plug manufacturers say specifically to NOT gap iridium or platinum plugs, only copper. They come "pre-gapped" out of the box. So whoever puts the plugs in an the Cruze factory doesn't check, why would they?
> 
> The disconnect is between Chevy and NGK. The spec plug is out of spec. And I will bet if you did a careful test on the rest of your car you will find much more even further out of spec, lol. Calm down on the end of the world conspiracy stuff on your .010 spark plug gap.


:sigh:

Agreed. I don't think that most non-enthusiast users will know or care as long as the car goes. If somebody suddenly starts to care because their job relocated 50 miles away instead of 15, that's when they'll look up this issue.


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## Chevy Customer Care (Oct 29, 2011)

H3LLON3ARTH said:


> What will you be able to do about this problem.
> 
> Sent from my Droid




H3LLON3ARTH,
I can document everyone's case to ensure that GM is made aware of this issue. I can get the customer's into a dealership that are not able to fix this issue or that would rather have a dealership do it for them. I am here to assist people with getting their vehicle issues taken care of. If you have any other questions please feel free to contact me.
Thank you,
Stacy Chevrolet Customer Service


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## Snuze (Nov 6, 2011)

sciphi said:


> :sigh:
> 
> Agreed. I don't think that most non-enthusiast users will know or care as long as the car goes. If somebody suddenly starts to care because their job relocated 50 miles away instead of 15, that's when they'll look up this issue.


I think though, you see a lot of people coming in here, complaining about issues with their car, like hesitation, lack of power, etc. Re-gaping plugs seems to clear all that up, and it's something that should be correct from the factory. So I think the flip side is that having them set properly, from the factory, would eliminate a lot of issues people are having.


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## Ragin Cajun (Feb 11, 2012)

Ill check mine tomorrow but I can't believe that opening the plugs up a few thousandths is going to get rid of anyone's lack of power or hesitation issue. I can understand the plugs being slightly out of spec but things do change down the line and there is a possibility that the gap was changed without being correctly documented.


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## Chevy Customer Care (Oct 29, 2011)

rbtec said:


> Stacy,
> Can you look into the issues with coolant leaks/smell? This seems to be a major issue and many people would like to know what GM is doing about it. I'm sure that lots of people, including myself, feel like the Cruze is a ticking time bomb with all these issues people are having.
> 
> 
> Sent from my Autoguide iPhone app





rbtec,
I, as well as others, have made GM aware of this issue. They are working on finding a solution. Unfortunately at this time I do not have information as to where they are at in this process. I am very sorry for this inconvenience to you. I will keep you posted as I get information. If you have any other questions, please feel free to contact me.
Thank you,
Stacy Chevrolet Customer Service


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## Snuze (Nov 6, 2011)

Ragin Cajun said:


> Ill check mine tomorrow but I can't believe that opening the plugs up a few thousandths is going to get rid of anyone's lack of power or hesitation issue. I can understand the plugs being slightly out of spec but things do change down the line and there is a possibility that the gap was changed without being correctly documented.


You'd be surprised what a difference it can have. 

For the uninitiated, here's a little ignition primer: 

Basically your ignition is composed of a coil, a spark plug, and a two position switch. When charging, the computer flips the switch to supply the coil with power from the vehicle's electrical system. When the computer determines it needs to fire the ignition, the switch is flipped, putting the coil inline with the spark plug. This looks a lot like an LR (inductive-resistive) circuit. In our case the coil is L, the plug is R. Changing the gap of the plug is, in effect, changing the resistance of the circuit. LR circuits are governed by a "time constant," T = L/R. Opening the plug gap up, increasing R, makes T decrease. What this means is that the inductor (coil) discharges it's stored energy over a shorter period of time. This gives a very hot, intense spark, which can help raise combustion efficiency, meaning more power out of the same air/fuel charge in the cylinder. 

When gaping plugs, there's a few things to consider, and that's why I'm not crazy about all the comparisons people have made on here to boosted LS engines running 0.060" gaps. Our engine is a 4 valve per cylinder, pent roof style combustion chamber, where the LS is a 2 valve, with more of a wedge style. Our engine is designed for high tumble and swirl (remember those air dams in the intake manifold VT Tuner was messing with). This is used to help control emissions and raise efficiency by promoting more complete combustion. The LS has a different, and possibly less energetic charge motion, and may have a more powerful ignition coil, so it may be able to effectively run higher gaps, even under boost, while we cannot. 

If you want a more detailed breakdown on over and under gapping, here goes:

Now, when your spark plug fires, at the absolute very instant it happens, there's a potential difference between the electrode and the ground, and this ionizes the air in between, creating a more efficient path for spark travel, then the very next instant the spark jumps the gap. If your gap is too large, the swirling and tumbling effect can move the ionized gas particles out from that area between the ground and electrode. This means more energy is needed to jump the non-ionized gap, and you get a weaker spark, which leads to a lower temperature "flame kernel" (I'll explain more after the jump) and ultimately less efficient combustion. In extreme cases, with large gaps and very turbulent charge, the motion of the air fuel mixture can disrupt the spark itself, which is what's know as spark blowout. 

On the other hand, if your gap is too small, you have "weak" combustion. When the spark occurs, it creates a "flame kernel" between the ground and electrode. This flame is very hot, but very small, i.e. smaller in diameter than the gap in your plug. Now as we talked about earlier, the gap leads to determination of the discharge time constant, in this case making it longer. Since a finite amount of energy is going to be needed to create the flame kernel, the mixture motion can stretch or distort this kernel. It may not get hot enough to promote complete burn, or it could be stretched out and start combustion in multiple places in the cylinder at once. This could lead to some odd flame front propagation by "shielding" air/fuel mixture behind pockets of burned gases in the mixture and resulting in an incomplete burn. 

As for plug materials, here's what you should know:

The idea has been presented that gaps are narrowed for new engines so the plugs will reach maximum gap by the end of their 100,000 mile life. This is simply not true, for two reasons. One is materials - precious metal plugs have very high hardness and heat resistance, as has already been pointed out. However, the real detriment to spark plugs is spark erosion. Fortunately, precious metal plugs have very low rates of spark erosion. In one study traditional Cr-Ni plugs would open up from 0.7mm to 1.1mm in just 28,000km. Comparatively, platinum plugs only changed from 1 to 1.05mm in 100,000km. Another factor is design - precious metal is expensive, and modern plugs are designed using the "flow guidance principle." Only the very tip of the electrode is plated with an Iridium "anchor", while the sides are plated with "sacrificial" materials. The initial spark jumps from the iridium tip, but transitions to the sacrificial plates for the bulk of of the arc time, which is when the most plug erosion occurs. Thus the gap never change and all the wear occurs on the sides of the electrode. This is also a good reason to never use a "coin" type gap tool - it can damage or strip the Iridium tip. 

Now, I can't tell you what the proper gap is for the plugs, just how this all works. Since there are so many factors that affect combustion, it's different for every engine, or else we'd all run the same plugs and gaps. And clearly there's some "wiggle room." I haven't yet done the math to back it up, but I suspect a difference of 0.001" or so isn't going to make a huge difference. I do, however, believe that seeing a variance of 0.006" or more across plugs on the same engine indicates something is wrong in the supply or build chain over at GM. I'm also intrigued by the changing spec; my owners manual says 0.029", so I wonder why GM is now saying 0.033" to 0.037". I've talked to Vince briefly, who believes 0.025" to be a good, safe number, as it clearly still works, and mitigates the chances of spark blowout. I'd be interested in hearing if anyone on here has a tune and has increased their gaps, and what the outcome is.


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## XtremeRevolution (Jan 19, 2012)

Just got off the phone with Phillips Chevy in Frankfort, IL. 

They specified the following spark plug gap for the 1.4T: .033-.037. For the 1.8, they specified .028.

You may call them yourselves if you don't believe me.
815.469.2323 

I don't care what Vince says. I'm going by what GM specifically says they should be. Anyone in doubt is free to call the above number or your own dealer.

The correct and recommended spark plug gap is no longer up for debate. This is proven fact. If you want to argue it, call your dealer or GM and argue with them.

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## Snuze (Nov 6, 2011)

XtremeRevolution said:


> I don't care what Vince says. I'm going by what GM specifically says they should be. Anyone in doubt is free to call the above number or your own dealer.
> 
> The correct and recommended spark plug gap is no longer up for debate. This is proven fact. If you want to argue it, call your dealer or GM and argue with them.


Right on! If that's what the dealers are saying, than it's probably correct. I'm going to be swinging by my dealer on Saturday morning, I'll ask them, not because I doubt you, but just to get some more consensus. Also, just to be clear, I hope you don't think I'm fighting you on this, and my above post was meant more to be background information so that everyone would have an idea as to *why* this is an issue, and what can happen. 

In my previous line of work (helicopter parts logistics for the Navy), it was not uncommon to get out of spec parts. All our suppliers were supposed to supply things in a range of specs we specified in our contract, but that's not always how we got them. I suspect, as some have suggested, there has probably been a miscommunication between GM and it's supplier as to who is supposed to set the gap, with GM thinking the supplier is doing it, and the supplier thing GM is doing it. 

As far as it being a closed matter, I think for stock or near stock engines, you are absolutely correct. I still believe that for tuned engines, running higher than stock boost, the *potential exists* for this to be too much gap. An engine is a system, all the pieces and parts have to work together - changing one thing may necessitate other changes, but it may not, it's hard to say without testing. My cable should be arriving tomorrow. I'm planning to do some data logging in various states - stock gaps, all gaps set to 0.025", 0.030" and 0.035" (GM spec), first without tune, then with a tune. Hopefully someone with the know how to interpret that data will be willing to take a look at it and give us more insight as to what's going on.


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## XtremeRevolution (Jan 19, 2012)

Snuze said:


> I'm also intrigued by the changing spec; my owners manual says 0.029", so I wonder why GM is now saying 0.033" to 0.037". I've talked to Vince briefly, who believes 0.025" to be a good, safe number, as it clearly still works, and mitigates the chances of spark blowout. I'd be interested in hearing if anyone on here has a tune and has increased their gaps, and what the outcome is.


I think this logic is flawed, and I'm not referring to you specifically, but to the concepts described. .025 is good and safe and clearly works? For who? That is the bigger question. People are reporting hesitation, bogging, and lagging with .025. Mitigates the chance of spark blowout? Sure it does, it's tiny. .020 also mitigates the chance of spark blowout. .015 also does the same, as does .010. 

So why did he choose .025 specifically? From what someone else had said, it's because that's what the car rolled out of the factory with. That said, we've established beyond any shadow of a doubt that the car rolled off of the factory within incorrect gaps regardless of what the gap should be, because there is such a great inconsistency that it's not even funny. If we were to take Vince's advice, some would be gapping their plugs larger, some would be gapping them smaller, for what? A hunch? 

GM says .033-.037. That's what the car *should *have rolled out of the factory with. .035 is still small enough of a gap to mitigate spark blowout. In fact, I've driven 100 miles now on a .040 gap (my personal experiment), while scanning with Torque and saw now adverse effects or spark blowout.

I respect Vince and his work, but in this scenario, GM has the final say. The spark plug gaps were read directly from GM's service manual, and I saw AllData's specs with my own eyes, and they both say .033-.037. 

If Vince recommends .025 (which is a massive difference from GM's recommendation) for tuned Cruzes, he is free to do that as a case can be made for a smaller gap given the higher boost levels over stock. Non-stock boost calls for non-stock spark plug gaps. However, the stance of this forum and all of its members should be to follow GM's service manual and AllData when checking and gapping their plugs.


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## Ragin Cajun (Feb 11, 2012)

My owners manual states a gap of .029. It would be my guess that GM wrote that manual also. So who is wrong GM or those who write manuals for GM? The topic is still very much debatable whether you want to join or not. You seem to take personal offense when someone disagrees with you.

Can someone give me the NGK part number off of their pulg?


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## XtremeRevolution (Jan 19, 2012)

Snuze said:


> Right on! If that's what the dealers are saying, than it's probably correct. I'm going to be swinging by my dealer on Saturday morning, I'll ask them, not because I doubt you, but just to get some more consensus. Also, just to be clear, I hope you don't think I'm fighting you on this, and my above post was meant more to be background information so that everyone would have an idea as to *why* this is an issue, and what can happen.
> 
> In my previous line of work (helicopter parts logistics for the Navy), it was not uncommon to get out of spec parts. All our suppliers were supposed to supply things in a range of specs we specified in our contract, but that's not always how we got them. I suspect, as some have suggested, there has probably been a miscommunication between GM and it's supplier as to who is supposed to set the gap, with GM thinking the supplier is doing it, and the supplier thing GM is doing it.
> 
> As far as it being a closed matter, I think for stock or near stock engines, you are absolutely correct. I still believe that for tuned engines, running higher than stock boost, the *potential exists* for this to be too much gap. An engine is a system, all the pieces and parts have to work together - changing one thing may necessitate other changes, but it may not, it's hard to say without testing. My cable should be arriving tomorrow. I'm planning to do some data logging in various states - stock gaps, all gaps set to 0.025", 0.030" and 0.035" (GM spec), first without tune, then with a tune. Hopefully someone with the know how to interpret that data will be willing to take a look at it and give us more insight as to what's going on.


I know you're not fighting with me on this. It's all in good discussion. I replied as you were posting the above, and I hope you don't think I'm fighting with you. I can come off with that tone without wanting to. I'm just taking a stand for what the truth is so that nobody has the slightest doubt as to what their cars should be set to. 

I agree with everything else you have said and couldn't have said it better myself.


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## XtremeRevolution (Jan 19, 2012)

Ragin Cajun said:


> My owners manual states a gap of .029. It would be my guess that GM wrote that manual also. So who is wrong GM or those who write manuals for GM? The topic is still very much debatable whether you want to join or not. You seem to take personal offense when someone disagrees with you.


What date was your owner's manual printed? Is that owner's manual specifically for the 1.4L, or for both 1.4L and 1.8L? GM's service manual and AllData are more current and updated than your owner's manual. If I had to choose, I'd say GM's dealership service manual has the authority.

Explain to me how this topic is debatable when every dealership you call will specifically tell you that the *correct* gap is .033-037. Like I said, if you want to argue the fact, argue with GM, not with me, but there is no argument as to what the facts actually are, unless you don't believe that I actually called my dealer. If you don't, I provided the phone number above so you can do so yourself. 

Will you take your car in at 50-80k to replace the spark plugs, then pull them back out when you get home and close the gaps because you believe the dealership gapped them incorrectly?


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## XtremeRevolution (Jan 19, 2012)

Since we're on the topic, enter the Owner's Manual...

http://www.chevrolet.com/assets/pdf/owners/manuals/2012/2k12cruze.pdf

This manual lists .028 for both the 1.4T and the 1.8 motors. The manual is copyrighted 2011. Turns out there's a discrepancy even between owner's manuals if anyone is finding a .029 spark plug gap. 

I'm fairly certain the 1.4L spark plug gap in the owner's manual is printed in error. I suspect that if we thoroughly analyzed the owner's manual, we could find additional errors. 

For example, we know from the following post using tech data pulled directly from GM that the automatic transmission takes 8.0L or 8.5 quarts of transmission fluid:
http://www.cruzetalk.com/forum/34-1-4l-turbo/5888-manual-transmission-specs.html#post79869

The owner's manual says it takes exactly half that, listed as 4.0L or 4.2 quarts. Which one are you going to believe? The GM tech specs, or your owner's manual?


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## iKermit (Dec 13, 2010)

Instead of talking and argueing so much, you guys can just call the dealer...

/end thread


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## XtremeRevolution (Jan 19, 2012)

iKermit said:


> Instead of talking and argueing so much, you guys can just call the dealer...
> 
> /end thread


Thank you. That's the first thing I said this morning in this thread. I even provided the phone number to the dealer closest to me. Argue with your dealer if you must.


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## H3LLON3ARTH (Dec 16, 2011)

http://www.google.com/url?sa=t&sour...65jwDA&usg=AFQjCNGgW80MpFyFCGdovLzgvinRTVdQ5A

I'm going to index my plugs this weekend

Sent from my Droid


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## Ragin Cajun (Feb 11, 2012)

I just called NGK and they said that this plug was made specific for the 1.4 and the correct gap is indeed .027. He also stated that the ignition system wasn't designed for a larger gap due to resistance and the variable timing. I have a few calls in to local dealers also.


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## cecaa850 (Apr 9, 2012)

I've already had the dealer look it up. See page 7 of this thread. Spark plug gap for FE on the 1.4T


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## coinneach (Apr 10, 2012)

Ragin Cajun said:


> I just called NGK and they said that this plug was made specific for the 1.4 and the correct gap is indeed .027. He also stated that the ignition system wasn't designed for a larger gap due to resistance and the variable timing. I have a few calls in to local dealers also.


So we have the plug manufacturer saying one number and the car manufacturer saying something else. That's not encouraging.


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## Beachernaut (Mar 27, 2012)

I think some people may be getting the wrong impression about the differences in performance between .024 and .035.

After changing mine, I noticed a difference in low RPM hesitation. This can be misleading. If you read that as "I suddenly got more power", you're reading it wrong. I didn't notice more power. However, the power that is there is now smoother. This is most noticeable when shifting from 2nd to 3rd (I usually shift between 1800 and 2000 rpm). The vast majority of people driving this car will not notice.


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## XtremeRevolution (Jan 19, 2012)

Ragin Cajun said:


> I just called NGK and they said that this plug was made specific for the 1.4 and the correct gap is indeed .027. He also stated that the ignition system wasn't designed for a larger gap due to resistance and the variable timing. I have a few calls in to local dealers also.


Call them back and ask them why the gaps are all over the place, from .019 to .029 among different owners and even different gaps in the same motor. I'm sure they'll have a wonderful explanation why a plug that's usually supposed to be pre-gapped is so severely inconsistent that it's beyond the point of "laughable." 

Then, have your dealer's service department on the line while you do this so NGK can explain to them why they're wrong and should instead be gapping the plugs to .027 instead of what AllData and GM's service manual states. If you could get GM's customer service on the line, you might have some fun as well.

Lastly, before you get off the phone with them, have them email, fax, or snail mail you documentation stating (in writing) that the spark plug gap should be .027. It would also be nice for them to explain to you what spark plug gap has to do with variable timing.


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## coinneach (Apr 10, 2012)

XtremeRevolution said:


> Then, have your dealer's service department on the line while you do this so NGK can explain to them why they're wrong and should instead be gapping the plugs to .027 instead of what AllData and GM's service manual states. If you could get GM's customer service on the line, you might have some fun as well.


If your idea of fun is two engineers and a CSR all screaming epithets at each other, sure.


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## jblackburn (Apr 14, 2012)

> If your idea of fun is two engineers and a CSR all screaming epithets at each other, sure.


Sounds more interesting than some of the crap they call TV these days.

Whatever the spec is, it still doesn't explain why the **** mine were gapped so low (.020-.022" for most of them!)


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## XtremeRevolution (Jan 19, 2012)

Nevermind, I went ahead and called them. I have them on the line as I'm writing this. 

2011 Chevy Cruze. Preset gap was .027 or .028 for both the 1.8L and 1.4L Turbo motor. Spark plug gap number is IFR7X-7G, where the 7 refers to a pre-set gap. GM for some reason saw it unfit to use a different spark plug gap for the 1.4L Turbo motor than they did for the 1.8L motor off the line. NGK couldn't comment on exactly why this was so; they simply stated that this is what GM ordered, but made it very clear that GM did not check or gap the plugs before installing them. They were installed as is. 

They stated they do not have information for the 2012 Chevy Cruze, only the 2011.

In any case, GM may at some point have discovered that .027/.028 was not the ideal spark plug gap, and raised it to .033-.037, which I'm assuming is what AllData is based off of.


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## obermd (Mar 3, 2012)

parish8 said:


> i dont trust my butt meter at all but there are so many people here reporting an improvement in low rpm driveability i am starting to believe.... cant wait for the mileage reports to come in.


Butt meters are the best way to tell if a car is running smoothly.


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## Ragin Cajun (Feb 11, 2012)

XtremeRevolution said:


> Nevermind, I went ahead and called them. I have them on the line as I'm writing this.
> 
> 2011 Chevy Cruze. Preset gap was .027 or .028 for both the 1.8L and 1.4L Turbo motor. Spark plug gap number is IFR7X-7G, where the 7 refers to a pre-set gap. GM for some reason saw it unfit to use a different spark plug gap for the 1.4L Turbo motor than they did for the 1.8L motor. NGK couldn't comment on exactly why this was so; they simply stated that this is what GM ordered, but made it very clear that GM did not check or gap the plugs before installing them. They were installed as is.
> 
> They stated they do not have information for the 2012 Chevy Cruze, only the 2011.


I can't say why the gaps are incorrect from ngk. But I believe they have the correct gap info and that there is an issue with dealers having different specs.


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## XtremeRevolution (Jan 19, 2012)

coinneach said:


> If your idea of fun is two engineers and a CSR all screaming epithets at each other, sure.


I'd love to be in that position. 



Ragin Cajun said:


> I can't say why the gaps are incorrect from ngk. But I believe they have the correct gap info and that there is an issue with dealers having different specs.


Well, humor me here. They (NGK) specify .028/.029 gap. There's only one person I know of that actually measured a .029 gap in their Cruze, and it was the person who inspired me to start the first thread regarding best gap for FE. 

What's interesting to note is that people are in fact getting bogging, lagging, and hesitation with the gaps their cars are currently gapped to. We know that this type of behavior can be caused by a variety of reasons that may not be related to spark plug gap. 

We do know GM specifies .033-.037. You will never take your car to NGK to get your spark plugs changed, but people will in fact be taking them to GM to get them changed. When they do, GM will gap them as the service manual specifies. 

We have two possible scenarios. Either the car will run better with the GM specified gap, or the car will run worse. Back to the bogging, lagging, and hesitation issues, we are finding that everyone who increases their spark plug gap to .033-.037 has noticed a sudden absence of this behavior. If that doesn't raise a red flag, it should. One would be hard pressed not to ask themselves why people are experiencing these benefits when increasing spark plug gaps to what GM specifies instead of what NGK claims they pre-gapped them to. I say claims because we've proven they did a piss poor job of it. 

I would like to bring to light the undeniable fact that NGK is merely a *vendor*. They didn't design the car, nor the motor, nor the ignition. They were given a spec by GM and they followed it (poorly) and delivered spark plugs as they were paid to. If I recall, LuK was also contracted to produce clutches, and they failed miserably at that for the 2011 model year. If we are trying to determine which of these companies (the car's manufacturer-GM or a vendor-NGK) to believe, I don't see any reason to crown the vendor as the superior authority and more reliable source of information. Quite the contrary, they were only given a simple spec and paid to produce it. Let make make clear that NGK is not giving a recommendation, but simply stating what they were told to gap these to and what the car was supposed to come with from the factory. If they gave a recommendation, they would be in direct opposition of what GM is stating. When it comes to warranty and liability concerns, they will err on the side of caution and advise that you contact your dealer. 

GM's engineers and writers of the service manual were the ones who actually designed the car.

I'm tempted to follow up with Stacy regarding this issue and have her create a case for this and look into it for me as she offered to. Given what the service manual states, I'm almost entirely sure of what her recommendation will be: "let me set up an appointment with the dealer for you to take it in." I would then have to take my car to the dealer. Take a quick guess as to what spark plug gap they'll set. I'll give you a hint, it won't be below .030.

You are free to plug your gaps to whatever you want to. However, every Cruze that has its spark plug changed from this day forward will be gapped between .033 and .037 by the dealer and by every mechanic's chop. They will not consult with NGK to verify. If anything, they will consult with GM, and we know what their recommendation is.


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## H3LLON3ARTH (Dec 16, 2011)

Well I just pulled my plugs they were all around. 25 I bumped them up to. 33 and this weekend I'm indexing them.

Sent from my Droid


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## 70AARCUDA (Nov 14, 2010)

H3LLON3ARTH said:


> Well I just pulled my plugs they were all around. 25 I bumped them up to. 33 and this weekend I'm *indexing* them.
> 
> Sent from my Droid


...what process are you using to achieve that *indexing:* 'stacked gaskets' or simple 'twist-to-fit'?


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## E7Hartman (Mar 16, 2012)

Having a 2012 Eco (AT) I would be extremely interested to see if what the gaps are. Knowing in advance that this may only really effect MT cars the most, I would still like to see what the dealer finds. I have less then 3200 miles on this car and if by tweeking small things save even $5 a week in fuel, its still a savings of MY $. Does Stacey need to be the one to contact my dealer to look at this?


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## XtremeRevolution (Jan 19, 2012)

E7Hartman said:


> Having a 2012 Eco (AT) I would be extremely interested to see if what the gaps are. Knowing in advance that this may only really effect MT cars the most, I would still like to see what the dealer finds. I have less then 3200 miles on this car and if by tweeking small things save even $5 a week in fuel, its still a savings of MY $. Does Stacey need to be the one to contact my dealer to look at this?


No, you should be able to just take your car in and tell them you've read reports of a 100% error rate between what the spark plugs have and what's in their service manual, and you want them to check it for consistency and accuracy.


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## E7Hartman (Mar 16, 2012)

Excellent...thanks


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## H3LLON3ARTH (Dec 16, 2011)

70AARCUDA said:


> ...what process are you using to achieve that *indexing:* 'stacked gaskets' or simple 'twist-to-fit'?


Inserts I'm buying a kit.
http://www.google.com/url?sa=t&sour...65jwDA&usg=AFQjCNGgW80MpFyFCGdovLzgvinRTVdQ5A

Sent from my Droid


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## SlvrECObullet (Feb 21, 2012)

Well I'm Here to report my findings... 
1) in my owners manual iat say's the spark plug gap for the 1.4L and 1.8L should both be .028 for some reason. 
2) The SPG that was from fractory are: .024, .028, .026, .027. That is from Left to Right looking at the engine from the front. 
3) I change the SPG to .036, drove around the block and noticed a bit better throttle response.
4) Recommend every person checks there gap whether 1.4L or 1.8L and make sure the Gap is to GM Specs listed in this thread.

Holla!!! Now time to Send GMCSR Stacy about my findings, everyone should be either sending her your findings or contacting GMCS.


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## Snuze (Nov 6, 2011)

H3LLON3ARTH said:


> Inserts I'm buying a kit.
> JEGS Spark Plug Indexing Kit - JEGS
> 
> Sent from my Droid


Uhh... You know you can get a Sharpie and some washers and achieve the same thing, right? That's $40, and you still don't get the washers!

Besides, when you index them, how are you going to do it? Which direction will the J tip point?


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## 70AARCUDA (Nov 14, 2010)

H3LLON3ARTH said:


> Inserts I'm buying a kit.
> JEGS Spark Plug Indexing Kit - JEGS
> 
> Sent from my Droid


...excellent, you're doing it the "correct" way!

FWIW you'll probably notice about 1-5% increase in hp (see #4) with the _extra_ 2-5% coming courtesy of the turbo's higher operating CR: http://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp

The old MOPAR dual-plug HEMI™ engines "love" indexing.


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## H3LLON3ARTH (Dec 16, 2011)

70AARCUDA said:


> ...excellent, you're doing it the "correct" way!


Yes sir thats the only way to do it I'm hoping it will give me better MPG and throttle response I'll let talk know after a couple of tanka of gas.

Sent from my Droid


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## H3LLON3ARTH (Dec 16, 2011)

Snuze said:


> Uhh... You know you can get a Sharpie and some washers and achieve the same thing, right? That's $40, and you still don't get the washers!
> 
> Besides, when you index them, how are you going to do it? Which direction will the J tip point?


Well I want to do it right and this is what was recommended to me by a really good mechanic at the shop I work at and hes helping me do it I think it will be facing towards the intake 

Sent from my Droid


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## Campuscop2003 (Mar 5, 2011)

Plugs are done, my results
1.8L N/A Engine

#1 - .19
#2 - .24
#3 - .22
#4. -.24

Re-gapped to Gm's spec of .28
Haven't driven it yet, will report back when I do with my thoughts.


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## parish8 (Mar 11, 2012)

this is only slightly related to this thread since the ls1 is an entirely different engine. also most of the talk is on stock tuned engines. 

the typical gap from the dozen or so boosted ls1's i have had is ~035 up to 10psi, ~025 up to 18psi. above 18psi and i saw spark blow out on more than one set up. ls1's have some stout coils. hptuners and efilive both allow you to adjust the dwell for a hotter sparks and this helps when over 20psi without having to gap the plugs any tighter than 025.

i am not exactly sure what condition causes spark blow out. i think it has to do with the density of the charge that has to be ignited. an 6.0 ls motor at 20psi and a 1.4 ecotech at 20psi may have a vastly different intake charge density. 

that being said i still see i see a strong possibility for spark blow out on a tuned car(20psi?) if the plugs are gaped at .033-.037.


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## XtremeRevolution (Jan 19, 2012)

parish8 said:


> this is only slightly related to this thread since the ls1 is an entirely different engine. also most of the talk is on stock tuned engines.
> 
> the typical gap from the dozen or so boosted ls1's i have had is ~035 up to 10psi, ~025 up to 18psi. above 18psi and i saw spark blow out on more than one set up. ls1's have some stout coils. hptuners and efilive both allow you to adjust the dwell for a hotter sparks and this helps when over 20psi without having to gap the plugs any tighter than 025.
> 
> ...


One thing someone else mentioned here is that it's not the PSI that makes the slightest difference, but rather the airmass you're moving through the cylinders. I could put 14psi through my L67 3.8L engine and I won't be going as fast or creating anywhere near as much power as I would if I put 14psi through the 3.8L engine we find in the Nissan GTR if you catch my drift. It's not a matter of how much pressure you're building, but how much air you're moving. 

As you mentioned, the spark plug gap for tuned and higher boosted motors will vary, but considering I'm not experiencing any spark blowout with spark plug gaps set to .040, I'm hardly seeing .025 as _necessary_. I could be wrong, but I have yet to hear of someone actually testing this. Prior to these recent threads, nobody _I know of_ even bothered to think about what spark plug gap they were running. 

I think someone with a tune needs to just gap up to .035 and let us know if there's any spark blowout. Absolute worst case, there's misfiring and the spark plug gap is deemed to be too large, and said person can take it down to .033, .031, .029, and so on to see where the misfires stop. 

My _suspicion _is that .035 won't be a problem with Trifecta tuned cars.


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## Starks8 (Jul 20, 2011)

I thought somebody was going to do a 'How-To' video for this? The pictures were somewhat helpful but i learn best by watching others do it and then replicating it. It would be a great thing for us novice car/ do it yourself-ers. A big thanks in advance for anybody willing to do a step by step video for all of us!


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## coinneach (Apr 10, 2012)

For grins, this morning I replaced my factory NGKs with new Autolite iridiums. I gapped them to .030*, went for a longish drive, refueled, ran some errands and went to work, then came home. Performance and fuel economy loss *CONFIRMED*; 1st and 2nd feel slow as February molasses now and I'm getting 30mpg indicated city**. Bumping them back to .035 first thing tomorrow. Once my Trifecta is installed and tweaked, I may play with the gap more and get some objective numbers via datalogging.

*: Little Old Autozone Lady Cashier told me, "They're already gapped, no need to worry about that." Ha. Also, HA. Yeah, they were gapped: .045.
**: I know, kri moar about only getting 30 city in a car rated for 25.


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## boats4life (May 28, 2011)

SlvrECObullet said:


> Obviously someone at the plant is not doing there Job properly and QA checking the plugs before they get installed. Or its possible they QA check a handfull out of a TON... and saying GTG.


This seems like a very good explanation- and I like the QA reference, lol. FOD free engine bay FTW.


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## Patman (May 7, 2011)

According to my owner's manual both engines are set at .028. I will check mine tomorrow when the engine cools down.


Without digesting all 14 pages of posts on this subject: Does a wider gap help the MPG and HP?


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## haoleboy (May 9, 2012)

Gapped the plugs tonight. Had 1 at .024 and the other 3 at .025. Put them all back in and started it but didn't drive it. I also took out the resonator pipe below the airbox so its gonna be hard to tell which made the biggest difference.


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## XtremeRevolution (Jan 19, 2012)

coinneach said:


> For grins, this morning I replaced my factory NGKs with new Autolite iridiums. I gapped them to .030*, went for a longish drive, refueled, ran some errands and went to work, then came home. Performance and fuel economy loss *CONFIRMED*; 1st and 2nd feel slow as February molasses now and I'm getting 30mpg indicated city**. Bumping them back to .035 first thing tomorrow. Once my Trifecta is installed and tweaked, I may play with the gap more and get some objective numbers via datalogging.
> 
> *: Little Old Autozone Lady Cashier told me, "They're already gapped, no need to worry about that." Ha. Also, HA. Yeah, they were gapped: .045.
> **: I know, kri moar about only getting 30 city in a car rated for 25.


I seriously laughed out loud reading this, LOL. Thanks for putting me in a good mood.


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## whatsstuckk5 (Mar 4, 2012)

parish8 said:


> this is only slightly related to this thread since the ls1 is an entirely different engine. also most of the talk is on stock tuned engines.
> 
> the typical gap from the dozen or so boosted ls1's i have had is ~035 up to 10psi, ~025 up to 18psi. above 18psi and i saw spark blow out on more than one set up. ls1's have some stout coils. hptuners and efilive both allow you to adjust the dwell for a hotter sparks and this helps when over 20psi without having to gap the plugs any tighter than 025.
> 
> ...


this man KNOWS boosted motors. if you dont believe me, search his user name on youtube and watch some videos of his silverados. absolutely nuts. 

that being said, I gapped mine to .35 and have put 500 or so miles on. mileage is definitely no worse and its smoother power down low. Whenever I tune it, i will probably drop the gap back down to .030 or so, but for now, it works at the stock 15 psi. Another thing, 98% of the rpm my car sees are under 2500 rpm, and even then most are under 2000 rpm so I will take what I can get that is useful in 95% of my driving.


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## XtremeRevolution (Jan 19, 2012)

whatsstuckk5 said:


> this man KNOWS boosted motors. if you dont believe me, search his user name on youtube and watch some videos of his silverados. absolutely nuts.
> 
> that being said, I gapped mine to .35 and have put 500 or so miles on. mileage is definitely no worse and its smoother power down low. Whenever I tune it, i will probably drop the gap back down to .030 or so, but for now, it works at the stock 15 psi. Another thing, 98% of the rpm my car sees are under 2500 rpm, and even then most are under 2000 rpm so I will take what I can get that is useful in 95% of my driving.


Don't diesels not use spark plugs? 

Haha, just messing around. I can definitely tell he knows what he's talking about. We can use as many experienced car nuts as we can get!


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## kevjam79 (Mar 18, 2011)

> rbtec,
> I, as well as others, have made GM aware of this issue. They are working on finding a solution. Unfortunately at this time I do not have information as to where they are at in this process. I am very sorry for this inconvenience to you. I will keep you posted as I get information. If you have any other questions, please feel free to contact me.
> Thank you,
> Stacy Chevrolet Customer Service


Stacy - Please keep us up to date.

Kevin


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## sciphi (Aug 26, 2011)

Xtreme, I thought you were tuned for some reason. It's news to me that you're running a stock tune.

Anyhow, in the normal mode of the tune, the slightly larger gap works just fine. I regapped mine to 0.030-0.032" with no ill effects in a few hundred miles of driving. There's a definite boost in power down low, like between 1000-1500 RPM's. I can't tell a difference with the engine running under heavy boost. It's under vacuum or light boost conditions at low RPM's where the biggest difference has been noticed, at least with my tuned Eco MT.


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## XtremeRevolution (Jan 19, 2012)

sciphi said:


> Xtreme, I thought you were tuned for some reason. It's news to me that you're running a stock tune.
> 
> Anyhow, in the normal mode of the tune, the slightly larger gap works just fine. I regapped mine to 0.030-0.032" with no ill effects in a few hundred miles of driving. There's a definite boost in power down low, like between 1000-1500 RPM's. I can't tell a difference with the engine running under heavy boost. It's under vacuum or light boost conditions at low RPM's where the biggest difference has been noticed, at least with my tuned Eco MT.


Nah. My 95 Regal with the SC 3800 is tuned, but my Cruze is bone stock. Never could justify the $300-$500 (whatever the prices have bounced around between) for the tune. I'd love to do some testing and data logging for this, but I don't have the $300+ to do it. 

Anyone over at Trifecta need a sub box? lol.

In other news, I filled up gas today, after having driven 400 miles with a .035 gap and ~75 miles with a .040 gap. With a 31.3mph average speed, I achieved 43.8mpg. Running AC for 100 miles of that probably didn't help.


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## kevjam79 (Mar 18, 2011)

XtremeRevolution said:


> Nah. My 95 Regal with the SC 3800 is tuned, but my Cruze is bone stock. Never could justify the $300-$500 (whatever the prices have bounced around between) for the tune. I'd love to do some testing and data logging for this, but I don't have the $300+ to do it.
> 
> Anyone over at Trifecta need a sub box? lol.
> 
> In other news, I filled up gas today, after having driven 400 miles with a .035 gap and ~75 miles with a .040 gap. With a 31.3mph average speed, I achieved 43.8mpg. Running AC for 100 miles of that probably didn't help.


What was your average before?


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## XtremeRevolution (Jan 19, 2012)

kevjam79 said:


> What was your average before?


*43.8mpg @ 31.3mph* (.035 gap, 100 miles with A/C on)
*42.2mpg @ 29.5mph* (.035 gap, LOTS of stop and go traffic. Only 154 miles - partial fill-up)

42.8mpg @ 30.3mph
41.9mpg @ 33.5mph (~100 miles with A/C)
*43.8mpg @ 33.4mph* (~120 miles of highway driving)
*42.5mpg @ 32.7mph* 
41.3mpg @ 30.1mph
44.7mpg @ 32.2mph (first tank with 50psi in tires. Drove like a snail and never went past 2000RPM to see how far I could push it. ~100 miles of highway driving. First 500+ gallon tank)

All older fill-ups were in colder conditions so they won't really be valid. 

I'd say if we compare to the tanks that were the most similar with regard to average fuel economy, you'll find that the average speed on the tanks with the new gaps was significantly lower.


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## OnlyTaurus (Mar 20, 2012)

Makes me wonder if GM have the gaps backwards between the LUW and LUJ. After doing some research, it seems .025 is better for turbo applications(for blowout reasons, obvously), so maybe the 1.4's were supposed to have the .025 spec and the 1.8's should have the .033-.037 spec. Makes sense to me. ??


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## XtremeRevolution (Jan 19, 2012)

OnlyTaurus said:


> Makes me wonder if GM have the gaps backwards between the LUW and LUJ. After doing some research, it seems .025 is better for turbo applications(for blowout reasons, obvously), so maybe the 1.4's were supposed to have the .025 spec and the 1.8's should have the .033-.037 spec. Makes sense to me. ??


GM didn't specify a .025 spec anywhere. That was Vince's idea. GM paid NGK to spec to .028 on all motors. GM's service manual states .033-.037 for the 1.4T and .028 for the 1.8N/A. 

It would make sense to me to run the 1.8 at the same spec as the 1.4T if not larger. I have no idea why they spec'd it so low.

While analyzing this, we have to try to figure out why they did this, not to find reasons why other similar things have happened and try to make them fit into this equation. For example, we would be inclined to believe that GM stated .028 from the factory for spark blowout reasons. However, one must ask themselves at what gap the spark blows out on this motor if that was the reason. I've been driving at .040 without any spark blowout or abnormal behavior, so I have a very difficult time believing that .028 was specified for spark blowout reasons.

I wouldn't put it past GM to make a mistake like that. They've done worse things in the past, but I don't think that's the case here.


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## OnlyTaurus (Mar 20, 2012)

XtremeRevolution said:


> GM didn't specify a .025 spec anywhere. That was Vince's idea. GM paid NGK to spec to .028 on all motors. GM's service manual states .033-.037 for the 1.4T and .028 for the 1.8N/A.
> 
> It would make sense to me to run the 1.8 at the same spec as the 1.4T if not larger. I have no idea why they spec'd it so low.
> 
> ...


I meant .028. My fault. If it were to be tested, it'd probably be a good idea to have someone with the tune do the test. 20psi is a lot of pressure in the cylinders, therefore more cause for blowout. You may not have the tune yet but you said you wanted to eventally, and when you do, your opinion may change with the gaps.


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## coinneach (Apr 10, 2012)

XtremeRevolution said:


> GM didn't specify a .025 spec anywhere. That was Vince's idea. GM paid NGK to spec to .028 on all motors. GM's service manual states .033-.037 for the 1.4T and .028 for the 1.8N/A.


What's really funny (as in weird, not lol) about that is, I just looked in my owner's manual and it calls out .028 for both engines. Someone, maybe multiple someones, dun goof'd.


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## 70AARCUDA (Nov 14, 2010)

...that's *why* I said we need to ask GM what the gap *SHOULD* be, NOT just go by what they seemingly incorrectly have printed in the Owners Manuals.



70AARCUDA said:


> ...ah, but the "real" question should be: _"...what does *GM* specify the gap *should* be?"_


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## XtremeRevolution (Jan 19, 2012)

70AARCUDA said:


> ...that's *why* I said we need to ask GM what the gap *SHOULD* be, NOT just go by what they seemingly incorrectly have printed in the Owners Manuals.


Call your dealer. I'm sure the service manual is more current than anything else we could get our hands on.

Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


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## Patman (May 7, 2011)

Earlier today I pulled out the plugs on my 1.8 and replaced them with Autolite XP3923s Iridium gapped at .035 what a difference!! Kinda like after I tuned. Where did the power come from. The NGKs were not that bad(carbon on them)after 19000 miles. Would have bought AC Delco Iridium but they are not avail. in Cincinnati(even at the AC Delco distributor where I get my filters). X, thanks for putting this thread out. Got me to do something I would not have thought about doing until @35000 miles. Also got me motivated to check the plugs in my wife's Mailbu. I replaced them with AC Delco Iridium last year so I just cleaned them up and regapped them. I am surprised all the parts stores and even Rockauto say to gap at .025 the manual says .028. I truly think no one understands this car/engine. Kinda like one of those anything goes situations as long as it makes sense or it is somewhat close to reasonable.


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## XtremeRevolution (Jan 19, 2012)

Patman said:


> Earlier today I pulled out the plugs on my 1.8 and replaced them with Autolite XP3923s Iridium gapped at .035 what a difference!! Kinda like after I tuned. Where did the power come from.


I have yet to hear of a single person who gapped to .035 and had negative results. Well done! Let's see if you can boost that fuelly rating!


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## OnlyTaurus (Mar 20, 2012)

OnlyTaurus said:


> Here.. if you guys did not know.
> 
> GM's specified gaps(directly from SI):
> 
> ...


These numbers are from Service Information.


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## XtremeRevolution (Jan 19, 2012)

OnlyTaurus said:


> These numbers are from Service Information.


Right. Pretty much the numbers every shop in the USA will reference when changing someone's spark plugs next time anyone takes their car in.


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## Patman (May 7, 2011)

XtremeRevolution said:


> I have yet to hear of a single person who gapped to .035 and had negative results. Well done! Let's see if you can boost that fuelly rating!


We'll see I know I heard Steve from Insane state he has heard people with the 1.8 getting @40 MPG on the highway. Right now I am sitting at 29.4 MPG as per the DIC. I have been doing a lot of highway driving. Remember I have that miserably inefficient 1.8 LOL. Seem to be doing OK by me tho. I hope it keeps going up.


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## sciphi (Aug 26, 2011)

Likely GM and/or NGK is okay with the spark plug gap at 0.025" since they figured they could save 5 cents a plug by not having them double-checked. For GM, it's one less potential supply-chain screwup to spec the same plug for both cars. For NGK, it's letting them churn out lots of identical plugs that can go in either engine. Lots of cost savings to be found there, and most folks won't ever notice the difference. Unless you're searching for a particular issue on a model-specific forum that is!


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## obermd (Mar 3, 2012)

Can the smaller gap cause the car to not perform as well on 87 octane fuel? A lot of us have had to go to 89, 91, and even 93 octane to improve the performance of our cars.


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> Can the smaller gap cause the car to not perform as well on 87 octane fuel? A lot of us have had to go to 89, 91, and even 93 octane to improve the performance of our cars.


Good question...

I'd love to know, but I'm not sure if I want to run back down to 87 octane for a week and a half to find out, lol.


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## Snuze (Nov 6, 2011)

obermd said:


> Can the smaller gap cause the car to not perform as well on 87 octane fuel? A lot of us have had to go to 89, 91, and even 93 octane to improve the performance of our cars.


In theory, the answer is No, since octane is merely a measure of detonation resistance, and that isn't affected by gap typically. That said, gasoline is a blend of many chemicals and additive packages, and some companies vary their additive packages between low, mid, and high grade. This can affect things like burn speed, heating value, and other parameters which coulda manifest themselves as smoother or rougher idle, and some power gain or loss. It's hard to say for sure that it is, or isn't true, but it seems to me that it's possible.


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## Skilz10179 (Mar 22, 2011)

whatsstuckk5 said:


> this man KNOWS boosted motors. if you dont believe me, search his user name on youtube and watch some videos of his silverados.


I used to be so in love with that truck! 5-6 years ago I used to watch those videos for hours on end.


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## weimerrj (Dec 4, 2011)

It seems EVERYONE is gapping their plugs now. Well done, Extreme for bringing this to light.

I just did mine this morning, and used the opportunity to teach my 9-year old how to inspect, check, and gap spark plugs. Also, tire rotation and the proper use of a torque wrench. It was a good man-day....for Mother's day anyway.

Yes, my plugs were all at .025. Opened them up to .034 and we'll see how things go. Gotta 200 mile drive tonight.


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## jblackburn (Apr 14, 2012)

Snuze said:


> In theory, the answer is No, since octane is merely a measure of detonation resistance, and that isn't affected by gap typically. That said, gasoline is a blend of many chemicals and additive packages, and some companies vary their additive packages between low, mid, and high grade. This can affect things like burn speed, heating value, and other parameters which coulda manifest themselves as smoother or rougher idle, and some power gain or loss. It's hard to say for sure that it is, or isn't true, but it seems to me that it's possible.


Actually I would bet to differ. My car ran like crap on 87 before. Out of curiosity, I put a tank of 87 in it (it was so cheap!) and then we took my car to Richmond last night. 

Stop and go traffic with AC on in 85+ degree weather is where my car always falls on its face, along with highway power. 

It did great! Felt just like it was running on 89 - just a smidgen less power than I saw on 93. 


Sent from my Autoguide iPhone app


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## Patman (May 7, 2011)

Despite it all, I filled up with 89 octane today. May be a "no no" since I am tuned but I am going to see how it goes this week since I changed the gap and new plugs. On this fill up I yielded 30.3 MPG out of my LS on 272 miles(mainly highway) and that was half 89 and 93. My car is probably saying "make up your mind"!!!! Typically when I don't use 93 from Shell the car feels like I need "feed the gerbils better" but this is 89 from Shell. I will post results the end of the week when I fill up again.


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## Snuze (Nov 6, 2011)

jblackburn said:


> Actually I would bet to differ. My car ran like crap on 87 before. Out of curiosity, I put a tank of 87 in it (it was so cheap!) and then we took my car to Richmond last night.
> 
> Stop and go traffic with AC on in 85+ degree weather is where my car always falls on its face, along with highway power.
> 
> ...


Sorry for the confusion, but what I was getting at was that it certainly may help. The higher octanes, with their different additive packages, may actually help a car with improperly gapped plugs run better. In other words, I think high octane fuel may help mask the problems caused by the plugs. Conversely, by setting your gaps correctly, it may help your car run better on 87 by allowing for more efficient combustion.


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## UpstateNYBill (Jan 14, 2012)

I have been following the other thread on this, but was not going to increase the gap because I did not want to affect emissions. However, now that it has become apparent that the gap is incorrect from the factory, I have gapped my plugs to factory specs as well.

Previously, they were at .026, .028, .028, and .027.


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## EcoCruzer (Mar 4, 2011)

I did mine today. Original gap was 24-26 and set them to .035" now. Took a short drive and there was no hesitation when cold. So far, so good. Will give it a few days to see how the MPG is affected. Right now I am running 87 octane.


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## XtremeRevolution (Jan 19, 2012)

Just a bit of a note I wanted to make. I changed the spark plugs on a co-worker's 2004 Toyota Matrix on Friday. He bought pre-gapped NGK Iridium plugs. Take a guess what gap his manual called for...

.043

I want to know why on Earth GM thought it would be necessary for the 1.8L N/A motor in the Cruze to run a .028 gap.


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## 70AARCUDA (Nov 14, 2010)

ECOmaniac said:


> .028 on a N/A engine would initially make me question the quality of the other ignition system components...particularly coils. I'd find it hard to believe though that the coils are that poor quality. I would guess that there was trade-offs made between emissions requirements and combustion efficiency as it relates to gapping. Just my guess...


...or, it could be that:

(A) the OEM plug maker simply "goofed" and *isn't* providing plugs gapped to GM's specifications?!?

...or:

(B) GM(USA) *doesn't* KNOW what the proper gap should be for the GM(Opel)-designed 1.4LT engine they're using?!?


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## Campuscop2003 (Mar 5, 2011)

Has anyone here looked at a Saturn Astra owners manual here? I just did and it says .035 gap. I was under the impression that these were the exact same engines?!? **** when I took the plastic piece up to do my plugs it said Saturn on it. I just thought that was interesting.


Link:
http://www.gm.ca/media/owners/manuals/2008_Saturn_Astra_Manual_en_CA.pdf


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## sedanman (Dec 10, 2010)

Well the manual states 0.028" spark plug gap. NGK set them to 0.027" gap. Looks like they are close to spec to me.

Also I think if a cylinder was misfiring the computer would be throwing codes.

GM probably specced these to 0.028" to make sure they would spark even when they get old as they have a 100,000 mile service life. Running these at the edge of tolerance of 0.037" does not sound like a good idea to me. 

You can do whatever you want, and if you have a problem you can always go back in and regap them if the gap widens too much after you put some miles on them.

I haven't checked mine yet but when I do I won't be changing the gap far off from the 0.028" recommended in the owners manual.

Butt dynos don't count.
Avg. MPG in uncontrolled conditions don't count.

There are a LOT of factors to engine performance and efficiency that will affect how it runs that make a far bigger difference than <0.010" in spark plug gap unless you're right on the edge and you cause a misfire which will be very obvious.

Having said that, it's all just theory until put into practice.


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## coinneach (Apr 10, 2012)

sedanman said:


> Well the manual states 0.028" spark plug gap. NGK set them to 0.027" gap. Looks like they are close to spec to me.


The owner's manual states .028. The service manual states .033-.037. And looking back over the thread, you can see that a lot of us have plugs that weren't set to .028 in the first place.


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## 70AARCUDA (Nov 14, 2010)

...from *Technical Data 10-3* of that 2008 Canadian Saturn Owners Manual: *1.8L L4 1 Automatic / Manual 0.035 in (0.90 mm)*


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## Campuscop2003 (Mar 5, 2011)

70AARCUDA said:


> ...from *Technical Data 10-3* of that 2008 Canadian Saturn Owners Manual: *1.8L L4 1 Automatic / Manual 0.035 in (0.90 mm)*



Says same thing in US Manual too, sorry didn't realize I posted the Canadian Manual, heres the us one:
http://www.saturn.com/content/dam/s...008/astra/2008-saturn-astra-owners-manual.pdf

Regardless it says .035


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## Cruze572 (Dec 20, 2011)

WOW! Finally got around to fixing this and its like a completely different car. While I really dont get on it too often so i dont know about the power difference from then to now, the horrendous hesitation that i had is completely gone and going up hills is much easier. I only wish i had known about this when i bought the car.


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## XtremeRevolution (Jan 19, 2012)

sedanman said:


> Well the manual states 0.028" spark plug gap. NGK set them to 0.027" gap. Looks like they are close to spec to me.
> 
> Also I think if a cylinder was misfiring the computer would be throwing codes.
> 
> ...


Have the last 17 pages of users not been enough of "put into practice" to demonstrate that there is a *VERY *noticeable improvement from increasing the spark plug gap to .035 on both the 1.8 and 1.4T? Or have you not actually read them all...

You're basically calling everyone idiots by saying that butt dynos don't count, implying that we're just imagining things because we want to. Can you be any more skeptical and pessimistic? The difference we're talking about isn't minor or debatable. It's not something you can shrug off as a placebo effect. Some guys have noted it feels just like they re-tuned their car. It's a big difference. 

Go ahead and believe your owner's manual if you want to. We've all proven here it's an unreliable source of information. Actually, I dare you to believe your owner's manual. Drain your transmission fluid (if you have an auto), and regardless of how much comes out, put only 4 quarts back in because that's what the owner's manual says it holds (nevermind the tech specs saying it holds 8 quarts). 

Let me know how it works out for you and what the transmission repair bill is. That would be one very expensive lesson on trusting your owner's manual. Also, on that note, don't take your car in to a dealer or a shop to have your spark plugs changed when it comes time to do so. You might have a big argument with them when they gap them to .033-.037 per the service manual or AllData (both of which are more current than your manual printed in 2011), assuming you have the 1.4T.

By the way, .010 increase in spark plug gap is *huge *no matter what car you're driving.


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## XtremeRevolution (Jan 19, 2012)

ECOmaniac said:


> You would have to be privy to the system engineering process and level of testing that goes into the development of a new automotive platform/subsystem/etc at GM or a subsidary to understand how robust their design processes really are and to understand how highly unlikely and frankly not even plausible your "A" and "B" really are. To suggest that the GM doesn't know what the sparkplug gap should be or that they allow suppliers to not only supply parts that do not meet their requirements specifications, but also allow them to be installed on hundreds of thousands of vehicles without verification...frankly, should be left to conspiracy theories.
> 
> Just because you tweak a plug gap and it provides a better throttle response and/or performance you think it justifies questioning their engineers and the design processes? In the automotive engineering world every decision is criticaly analyzed in theory and in the testing environment, there is no plug and play, guess and check, EVERYTHING is quantified and trade-offs are made in many arenas for many different reasons which in this case is left to speculation. Sparkplug selection and testing is carried out in a controlled environment - they did not just throw plugs into the bins on the assembly lines and say "here you go". I know this because I have designed breakout boxes that test GM assembly line components before they go into the next higher assembly. I would be willing to bet dollars to pesos that the sparkplug gap is verified against a known specification either on the floor or shortly prior to arriving at their final destination.
> 
> ...


Having demonstrated in the last 17 pages that this is not just remotely plausible, but actually happening, should make you think twice before telling us what the "facts" are unless you were actually there.

I have my own set of facts that there is zero argument or debate about:

Fact: NGK was contracted to produce spark plugs for the 1.8 and 1.4T, both of which are supposed to be gapped to .028

Fact: everyone is measuring anywhere from .018 to .029, which is a massive variance. Your claim that they didn't allow them to be installed in hundreds of thousands of vehicles without verification is frankly false. What more proof do you need than the fact that everyone is measuring them and finding that there is absolutely horrendous consistency. 

Fact: GM's service manual AND AllData calls for a .033-.037 spark plug gap on the 1.4T, which is in direct opposition to what NGK is claiming they should be (as if they are in any authority) and what is installed on everyone's cars. I have not seen a single person report that they pulled their plugs and they measured in the .033-.037 range. 

It is obvious to me that, similar to a few others here, you didn't read the entire thread. This was discussed in detail, so please go back and read it.


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## 70AARCUDA (Nov 14, 2010)

ECOmaniac said:


> ...Having worked through GM system engineering processes and having experience on the factory floors themselves, I can say with confidence that an oversight like you are suggesting is not even a remote possibility.


...ex-*GM*HE engineer here.

...and, Cruze steering wheels shouldn't have fallen off, nor PRNDL shifters incorrectly register, and transmissions shouldn't shift erratically, and Sonics shouldn't have been made/shipped/and sold that didn't have rear brake shoes, but they have, and continue to do so.

...so much for GM Quality Control being 100% effective.


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## XtremeRevolution (Jan 19, 2012)

70AARCUDA said:


> ...ex-*GM*HE engineer here.
> 
> ...and, Cruze steering wheels shouldn't have fallen off, nor PRNDL shifters incorrectly register, and transmissions shouldn't shift erratically, and Sonics shouldn't have been made/shipped/and sold that didn't have rear brake shoes, but they have, and continue to do so.
> 
> ...so much for GM Quality Control being 100% effective.


People shouldn't be having toxic coolant leaks into their cabin, the struts should never have started popping, the drum brakes should not have been "adjusted" to zero, the paint behind the rear doors should never have started chipping, the clutches up till November 2011 should never have been failing...

I and many others here can go on, and on, and on...


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## coinneach (Apr 10, 2012)

XtremeRevolution said:


> People shouldn't be having toxic coolant leaks into their cabin, the struts should never have started popping, the drum brakes should not have been "adjusted" to zero, the paint behind the rear doors should never have started chipping, the clutches up till November 2011 should never have been failing...
> 
> I and many others here can go on, and on, and on...


In any technical endeavour, there's engineering (what *should* happen), manufacturing (what *does* happen), and tech writers (what happened?).


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## XtremeRevolution (Jan 19, 2012)

ECOmaniac said:


> Yeah **** happens - there is a big difference between a design flaw rearing its head and complete ignorance - which is what you are suggesting.


I'm awaiting your explanation for the gigantic variance in the spark plug gaps everyone is measuring from the factory which SHOULD have been .028 on both motors. This isn't a design flaw here. It's NGK failing miserably to meet the specification tolerance for the spark plugs they were paid to make, and/or GM failing miserably to check the spark plug gaps before sending the cars on their way to the dealers. 

I'm also awaiting your explanation for why GM decided to fit the 1.4T motor with a .028 spark plug gap when their service manual now calls for a .033-.037 gap, and why they outfitted this 1.8L motor with a .028 spark plug gap when the Astra's 1.8L motor is specified for a .035 spark plug gap.


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## 70AARCUDA (Nov 14, 2010)

...to be honest, it simply sounds like the "new" *Global* GM hasn't got a clue about: (a) their *products*, (b) the *specifications* of those products, (c) the _incoming_ *QC* of farmed out parts for their products, or (d) the _outgoing _*QC *of their *final products*.


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## XtremeRevolution (Jan 19, 2012)

I went ahead and took the time to go through the three threads existing regarding this issue and make a compiled list of all of the measured spark plug gaps, and here's what I came up with. Interestingly enough, exactly 100 spark plugs and their gaps have been measured and recorded on this site, so the percentages shown are also the number of plugs measured. 

.019 - 2%
.020 - 11%
.021 - 0%
.022 - 4%
.023 - 3%
.024 - 27%
.025 - 33%
.026 - 8%
.027 - 2%
.028 - 6%
.029 - 4%

To interpret this, let me bring to light the following:

Vince at Trifecta says they should be .025 for ?
NGK says they should be .027 for both 1.4T and 1.8
Some owner's manuals say they should be .028 for both 1.4T and 1.8
Other owner's manuals say they should be .029 for both 1.4T and 1.8
GM and AllData say they should be .028 for the 1.8 and .033-.037 for the 1.4T. 
The Saturn Astra owner's manual says gap should be .035 for the 1.8.

If we are to assume that an acceptable tolerance is .001" above and below a given spec (a range of .002"), we would find that 68% of this sample size is within that tolerance, and 32% are out of that tolerance. 

If we are to assume that an acceptable tolerance is .002" above and below a given spec (a range of .004"), we would find that 73% of this sample size is within that tolerance, and 27% are out of that tolerance. 

If we are to assume that an acceptable tolerance is >.002", we should be checking and re-gapping our plugs for that reason alone. 

Pathetic.


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## 70AARCUDA (Nov 14, 2010)

...and, then there's the obvious discrepancies in their PUBLISHED spark plug gap numbers!

...sorta like how the 2011 Cruze Manuals states it's OK to *flat-tow *them behind an RV when it's not! Who does their "editing" these days?


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## obermd (Mar 3, 2012)

If the spark plug gap is causing many of us to run 89 or 91 octane to get descent performance from the engine it is a huge issue because of the additional cost of gas.

Personally I think it's just someone being sloppy at NGK and the guys at Lordstown not knowing there is an issue. If all the plugs were gapped at 0.028" as listed in the owners manual then we could easily chalk this up to a change in specification. But since the plug gaps are all over the map and none have been reported to be anywhere near either the owner's manual or service manual that is a sign of sloppy quality control somewhere.


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## 70AARCUDA (Nov 14, 2010)

...*facts* can be specified, measured, quantified, and _verified.
_
...*opinions* can be defended, argued and/or _ignored._


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## 70AARCUDA (Nov 14, 2010)

ECOmaniac said:


> Man EXTREME...you and 7AARCUDA are quite the tagteam - ever think of joining the WWF? I mean let's make smartass comments to everyone who posts something that doesn't align with your mode of thinking, that is *extremely mature*.


...is that _your_ *opinion* or _your_ *fact*?



...sorry, but the "kid" in me made me type that (but, the "adult" in me grinned as I did it)!


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## jblackburn (Apr 14, 2012)

My Volvos gap was specced at .028". When the gap got to be over .036" (copper plugs - it hate anything else), the thing would start misfiring at high RPM and was very buzzy at idle. 

My Cruze improved the way it drove entirely - and it's not just my imagination. More low end power and MUCH smoother idle. 

Yes, having gaps off by that much does make a difference - and not just on these cars. 

I seriously doubt they would design a car that intentionally bogged down so bad from a stop that it would almost stall. To me, this is absolutely how the car was designed to behave. 

Sent from my Autoguide iPhone app


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## XtremeRevolution (Jan 19, 2012)

ECOmaniac said:


> Dude you are way too tightly wound - You are obviously find this sparkplug issue to be a huge oversight, yet have you quantified what any of this actually means??? What is the actual difference in performance between a .028 gap and the .033 - .037 that makes it such a huge design flaw? Because your butt-dyno saw results you are professing this huge conspiracy theory about plug gaps and poor engineering on GMs part? Nowhere did I use the word "fact", you obviously have all of the answers and are on edge ready to hawk anyone and everyone who questions your threads/theories. Your attitude completely kills the desire to try and talk through something logically.





ECOmaniac said:


> I frankly think you are putting too much stock into this issue before actually quantifying how any of it is relevant in terms of performance.


Per my last post, the difference isn't between a .028 gap and a .033-.037 gap. 73% of people have measured between .023 and .027, so the difference is significantly larger than that. It *should* have been .028 according to the GM owner's manual. 20% so far are between .19 and .23. Is that big enough of a difference for you?

You brushing this off as mere opinion is a tad bit annoying to be completely honest. I apologize for the attitude, but I seriously doubt you could say you don't see where I'm coming from. So far, there is one person out of the 25 who have done this who said they didn't feel much of a difference. Just *one*. 

I don't claim to have all of the answers, but I do have some facts, and as far as I'm concerned, that's worth a lot more than what you have to say about GM's production tolerances. I didn't just say *my *butt-dyno. I said *everyone's* butt-dynos. *Everyone *is noticing a difference, not just me. *Everyone*. Did I say poor engineering? I said poor quality control and consistency. You don't have to use the word "fact" to speak as though what you're saying is fact. When you're ready to respond to the *facts *I've listed in the last two pages and talk about those, then I'll be more than happy to have a discussion, but this isn't a discussion. This is a pissing match about who claims they know GM's engineering departments and polices better. It's irrelevant when the facts right in front of you are in direct opposition. What more proof do you need that *someone* screwed up somewhere? 

How relevant is it? My car feels different. Very different. I've changed my shift points. People have adjusted their gaps and said "wow, now I can see how you shift as low as you do." People have stated an obvious and undeniable elimination of hesitation, lagging, and bogging they *consistently *experienced previous to this correction. For some people, it's a nice improvement. For many, it's a pretty big deal and completely change their perception of their car. That's not something you can just ignore.



70AARCUDA said:


> ...*facts* can be specified, measured, quantified, and _verified.
> _
> ...*opinions* can be defended, argued and/or _ignored._


Thank you.


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## XtremeRevolution (Jan 19, 2012)

ECOmaniac said:


> Man EXTREME...you and 7AARCUDA are quite the tagteam - ever think of joining the WWF? I mean let's make smartass comments to everyone who posts something that doesn't align with your mode of thinking, that is extremely mature.


I've been respectful so far. A bit argumentative and perhaps a bit abrasive in my tone of voice, but respectful nonetheless. I haven't insulted you or attacked you personally.

You want to know what would be extremely mature? Responding to peoples' posts without resorting to personal attacks.


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## XtremeRevolution (Jan 19, 2012)

ECOmaniac said:


> Still wondering what the purpose of the sparkplug gap arguement is, when by your own definition you and your sidekick haven't QUANTIFIED any of your claims about increasing the sparkplug gap or provided any solid data supporting anything that shows GMs allegedly screwy spark gap tolerances directly impact performance or economy. Sorry your butt dyno theories and 100 spark plug gap measurements from a site with varying experience, equipment and general knowledge don't represent DATA or FACT nor can the later be VERIFIED. Until you do, all you have is an opinion. But thanks for being a prick about it.


I find it amazing how we're the ones being pricks, but I'll leave that subject alone. I've had about enough of the personal attacks.


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> I went ahead and took the time to go through the three threads existing regarding this issue and make a compiled list of all of the measured spark plug gaps, and here's what I came up with. Interestingly enough, exactly 100 spark plugs and their gaps have been measured and recorded on this site, so the percentages shown are also the number of plugs measured.
> 
> .019 - 2%
> .020 - 11%
> ...


Actually - if the owners manual (0.028" +- 0.002") is correct, then only 20% of the plugs are in spec. If the service manual's 0.035" +- 0.002" is correct, then none of the plugs are in spec. Either way this is a real indicator that something is amiss in the manufacturing specification for the Cruze. Also, it's really interesting to note that none of the plugs are gapped above spec. All the plugs that are incorrectly gapped are below spec. I almost think there is a typo somewhere because if the spec sent to NKG was 0.025 +- 0.002 then 73% of the plugs are indeed in spec, with a bad shipment resulting in the 11% at 0.020".


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> Actually - if the owners manual (0.028" +- 0.002") is correct, then only 20% of the plugs are in spec. If the service manual's 0.035" +- 0.002" is correct, then none of the plugs are in spec. Either way this is a real indicator that something is amiss in the manufacturing specification for the Cruze. Also, it's really interesting to note that none of the plugs are gapped above spec. All the plugs that are incorrectly gapped are below spec. I almost think there is a typo somewhere because if the spec sent to NKG was 0.025 +- 0.002 then 73% of the plugs are indeed in spec, with a bad shipment resulting in the 11% at 0.020".


You've pretty much said it. The problem is that .025, as you noted, isn't the correct spec, even though that's a general average. It's .028 according to the most current owner's manual (made in 2011), and .027 according to NGK. It's a failure on all accounts and you hit the nail on the head.


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## XtremeRevolution (Jan 19, 2012)

ECOmaniac said:


> You are right man, you are right. The dynamic duo of sarcastic posts following mine couldn't ever represent a personal attack whatsoever...


Listen man, you're hung up about whether or not this can be quantified. You want proof as if we need proof to convince someone that this is making a big difference. We know something is wrong and these spark plugs are all gapped incorrectly. That's not news to anyone. At first you were arguing that GM didn't do anything wrong and were in disbelief that they would screw something up as badly as this. Well, if you had taken the time to read this thread, you would have seen that's not the case and not wasted your and everyone else's time. Now, you're trying to argue that this isn't making a difference. You're asking for proof. 

Want to know what proof I have? I have the facts that I've presented, and I have the fact that I've been making 2200+ no-bullshit posts on this forum with valid and useful information, so I'm not one to just make **** up and waste peoples' time doing something that won't benefit them in any way. I am one of many people on this board who's information is regarded with that kind of respect and we fully understand the importance of preventing misinformation. 

There is no misinformation for you to correct here. The spark plug gaps are incorrect no matter where you pull the spec from, and the aforementioned respected members of this community have chosen their words carefully when explaining the difference this makes.

You may form whatever opinions you would like to, but among those who have made this correction to their spark plug gap are two aspects that there is no question about:

1. they were incorrect to begin with
2. the correction made notable difference in performance at low RPMs that can be easily detected

If you want to quantify it, perform this correction on your car and spend the time to datalog and dyno test it. The rest of us find absolutely no need for that and would consider it a waste of time. It's a 15 minute procedure that yields immediate results.

If one person says it makes a difference, ask why. If two people say it makes a difference, do some research. If 24 out of 25 people and several respected and dedicated members of a discussion board say this makes a difference, guess what; it's extremely likely that it does make a difference. Nobody here has the time or money to spend to quantify the results so a couple of doubters could get the raw data they need to rationalize the 15 minute correction.


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## 70AARCUDA (Nov 14, 2010)

...an "in spec" spark plug gap ensures: (a) _intended_ engine performance, ie: power and economy and (b) _compliance_ with EPA emissions regulations.

...one "in spec" spark plug specification is it's *operational* gap, ie: what it_ starts _out with (gap widens with duration and wear).

...too *narrow* gap and _less_ than full ignition-coil *energy *(watt-seconds or Joules) is delivered to the air-fuel mixture, resulting in _under_ performance and _more_ than intended / permitted emissions.

...similarly, too *wide* gap and _less_ than full ignition-coil energy is delivered to the air-fuel mixture because the arc periodically fails to establish, resulting in mis-firing and poor performance and even _more_ emissions; and, with increased CR, possible "blow-out" of the arc.

...the "question" is: what gap does GM-Powertrain *intend* this engine to have (for intended performance & emissions), which, seemingly, they haven't (yet) got right in _their_ own publications (conflicting values) and in _their_ delivered vehicles (conflicting values).


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## sciphi (Aug 26, 2011)

I flipped the switch to sport mode today and went blasting uphill. There wasn't a funny transition around 2200 RPM like I'm used to getting, and the car accelerated like a scalded cat, faster than I remember. I've blasted up this hill 2x/week for the past 3 months, both in sport and regular modes. The hill rises about 500 vertical feet over the course of a mile, so it's pretty darned steep. This was the first time I blasted up it with correctly-gapped plugs and sport mode engaged. It had no problem holding 4th on a section of hill that usually needs 3rd, even in sport mode. There was a noticeable difference, namely that it was quicker, smoother, and could hold a lower gear to go up a particularly steep section.

There aren't any dynos nearby. Likely this wouldn't show up on a dyno anyhow since it's a driveability issue more than anything else. But to have almost everybody who's tried it and especially the nitpicky Eco MT crowd say it makes a difference, well, golly, there just might be something there.


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## obermd (Mar 3, 2012)

Stacy,

I think GM needs to start looking at Cruzes when they come in for any service, including oil changes. If there are a significant number of Cruzes with spark plug gaps out of spec as recorded by dealerships, this should become a TSB to all Chevy dealerships to check and correct each Cruze as it comes in for other service. Record both the incoming gaps and the gaps being set so that the same Cruze going for service later at any GM dealership won't have the same work done again. GM needs the incoming gaps to help figure out how to fix the issue, regardless of whether it's a GM, supplier, or both problem. 

The reason I think GM needs to have their dealerships do this check is to get a "corporate" verification of the problem. Although many of the members of CT are car enthusists who have the tools, knowledge, and experience to do a lot of their own maintainence and service, most are are not GM employees or therefore not "reliable" in the sense that GM's lawyers will require. In addition, there are hundreds of thousands of Cruze owners who are not able to do this. The check and correction for this obviously doesn't take very long once the engine has cooled down, so asking (and paying) dealership service departments to do this should not be an issue. Once the bulk of the Cruzes have been done, publicizing that this was done to build customer and non-customer goodwill will seriously help keep existing and acquire new customers.

I would also go so far as to say this needs to be checked at Lordstown before installing the plugs and then any Cruze assembled prior to the date Lordstown starts checking needs to have this done as part of the dealer prep.

There is already precedence for this. Flashing the automatic transmission ECUs to correct shifting issues probably took about the same amount of dealership service department time, plus it took a lot of software development, testing, and configuration management time. This will actually take less time and money to correct.

Just my 2 cents.


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## albow77 (Feb 18, 2012)

ECOmaniac said:


> Still wondering what the purpose of the sparkplug gap arguement is, when by your own definition you and your sidekick haven't QUANTIFIED any of your claims about increasing the sparkplug gap or provided any solid data supporting anything that shows GMs allegedly screwy spark gap tolerances directly impact performance or economy. Sorry your butt dyno theories and 100 spark plug gap measurements from a site with varying experience, equipment and general knowledge don't represent DATA or FACT nor can the later be VERIFIED. Until you do, all you have is an opinion. But thanks for being a prick about it.



Hey face it --- GM screwed up on this one. I was one of the first to try the regap and it is the best thing I have done. I loved the car but one of the major dislikes about the car was that it was very doggy from 1000 to 1700 RPM. The car would spit and sputter and then at 1700 rpm it would suddenly kick in and run good. I thought it was normal and accepted that the car was designed like that. ExtreamRev pointed out that the gaps were small and that he regapped to .035 and it ran better. As soon as I read that -- I went out and did it myself. It was the one thing that made my car near perfect now -- smooth power in the lower RPMs with no sudden jerky boost of power at 1700 rpm. It is because GM, for some reason, had the gap wrong or realized that the car will run better with the larger gap and changed the specs in the service manual later on. It really doesn't matter how or why the gap is incorrect but that my butt dyno has seen a major power improvement in low RPMs. If you want to try it you can and you can also report to this forum what changes if any you have noticed. Don't be knocking the people here because we don't know all the facts and can't show the dyno numbers. We will never know the truth on this subject from GM. This forum is here to help with issues and this is the biggest issue so far that may effect everyones Cruze. Everyone has reported that the car runs better after the regap. In my eyes GM messed up on this one not because the gap was incorrect/correct but from the wide range of the gaps that were reported here from everyone that checked. I would call that poor quality control and that is the fault of GM!


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## Gritts (Jan 23, 2011)

This spark gap issue caught my attention really fast. So I borrowed the old man's spark gap tool and proceeded to check my plugs. To my disappointment the gap tool I was using only went down to .035" Needless to say, it didn't fit at all, so I regapped at .035" and reinstalled the plugs. In my OPINION the car has more power--especially between 2nd and 3rd. Have not driven enough to get mileage numbers yet.

Before reading this thread, I noticed a gradual increase in mpgs and slightly more power from the 1.8 M6 which I assumed was do to the engine breaking in. (I now have abt. 14000 miles on the clock.) Could it have more to do with the plugs wearing? Current MPG is 36.1 mostly back road driving.

I am aware of the placebo effect of engine mods. (Everyone knows a car goes faster after a good washing!) *But I definitely think there is something to this spark plug issue. *I think this kind of information is what a forum is all about, it is up to the reader to decide if the information is valuable or not. It is why most of us are here to begin with. So a big THANK YOU TO THE OP!


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## albow77 (Feb 18, 2012)

Here is an update on the last 1000 miles with the plugs regapped. This tank was 87 oct and no eth. 427.1 miles and 9.79 gal = 43.6 MPG. The weather conditions were not in my favor. High cross winds half of the days and a 30+ mph headwind on one of the 35 mile trips to work. Otherwise it was calm. Not one single time this tank did I get a push from the wind. I also ran the AC for about 100 miles of this tank.

The last tank was 91 oct and no eth. 497.5 miles and 11.07 gal = 44.7 MPG. So my MPG has gone up some and it seems that premium gas maybe better than reg. 

Also had about 100 miles on the 3rd tank ago.

The last 2 tanks were after the regap and are my best 2 tanks so far. I could not tell the difference from one tank to the next on performance and the low RPM lack of power is gone. It is getting warmer so starting to run the AC more. I will still not confirm that the regap will give you better MPGs but will confirm it has not hurt the MPG. It could be the warmer weather or the car is getting broke in more. Just shy of 5000 miles on it. Just for fun I filled this tank with 89 oct E10 to see what that is like.


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## limited360 (May 6, 2011)

Warmer weather has the largest impact...


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## albow77 (Feb 18, 2012)

limited360 said:


> Warmer weather has the largest impact...



What about warmer weather and running the AC???


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## weimerrj (Dec 4, 2011)

I seem to see a bit of a MPG increase, and the low-rpm surge seems to have disappeared. That's after one day, so I'll reserve final judgement for the time being. 

But it seems I have more power throughout the powerband, so I think this is a qualified winner. 

Now, will GM/Chevy recognize that NGK is giving them spark plugs gapped well outside the required spec and fix this assembly problem? Can our resident Chevy customer service representative push this back to Lordstown?


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## XtremeRevolution (Jan 19, 2012)

ECOmaniac said:


> Yeah I should have read the entire thread - my apologies to XtremeRevolution - if you look at my original post my intentions weren't to bash anyone nor was I suggesting this is misinformation, it got a bit out of hand with the sarcasm/bantering about facts and opinions but I'll let that be. I'm going to ask some questions of the local stealership and see what they have to say. Personally I haven't checked my plugs and haven't had the slightest issue with low-rpm surge. I would be curious to see what happens on the higher RPM range on a bigger gapped plug though - if there would be a trade-off it would be on the high side. I would be hesitant to increase gap size on a tuned car as well, which may be why Vince @ Trifecta recommends a smaller gap size but that's just my guess. But from all of the testimonials it sounds like it's a good change overall for the DD though so I'll give it a shot.
> 
> I'll be on the dyno in the next week or so doing a baseline pull before I start modifying my car - as part of this I'll do a couple of pulls on the lower and upper ends of the gap "spec" and log some data to see how each gap size impacts the entire power band, fuel economy, RPM response etc. It would be interesting to be able to see just how much difference there is between the two conflicting gap sizes. Let me be clear here as well - this would be to support this thread so please don't question my integrity, I know how to dyno a car, test variables and log data so everything will be 100% objective.
> 
> ...


Apology accepted. We all get ahead of ourselves. The moderators know this to be true of me as well, lol. Sometimes we have a tendency to shoot from the hip when we get into a heated debate and say things we wouldn't have said the next morning. As long as it's for the better good, I don't mind it. 

To note, I also didn't have any issues with the low RPM lagging and hesitation, and mine were all gapped around .025. I was in fact getting respectable fuel economy numbers in the 41-42mpg range. Since I've increased this gap size, I've been consistently in the high 43mpg range but with more 'hazardous' fuel economy conditions such as lots of A/C, bad weather, and a lower average speed. I personally think it made a difference.

I recall Boats mentioning that Vince recommends to "leave them to what GM set them from the factory." I believe that at that point, he had assumed that the factory gap was .025, since that is where the vast majority of these came in. However, it's those 20% or so of people who are far under that point that are bringing this to such a great light. A gap of .020 or .019 is going to make a big difference, and those are the people who are really seeing these new gaps fix their hesitation, lagging, and bogging down. 

I'm very much looking forward to your results on the dyno. I would try them as low as .020-.022, as that's where some people are coming in, perhaps to try to replicate the conditions they're experiencing. That is, if you have time and can make enough runs. I don't question your integrity at all with this and trust you will report back with good information. If your results support what everyone has been seeing (which they should), it will pretty much be the nail on this argument's coffin. A decent sample size and some raw numbers should silence even the most skeptical nay-sayers. 

I too was a bit baffled when I discovered how big of an oversight this is. Based on the numbers I presented earlier for the gaps that have been recorded thus far, it's a huge oversight. To call it sloppy would be a compliment. 

I appreciate the time you've taken to write the above post. It shows some character, which is not something you find in a lot of people these days. Looking forward to having more discussions like this with you in the future, my friend.


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## danimal (Oct 4, 2011)

Just did my spark plugs tonight; 0.027, 0.026, 0.026 and 0.025. Re-gapped them all to 0.34. Maybe I will go a bit more, we''ll see if I can feel any difference in the ol' butt dyno this week. I already did the intake resonator mod a couple months back and it helped with gas mileage too! Hoping this spark plug gap will boost it more!


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## iKermit (Dec 13, 2010)

I think we should all go to the dealership and ask them to re-gap it. That way GM is made MORE aware of this issue.


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## obermd (Mar 3, 2012)

iKermit said:


> I think we should all go to the dealership and ask them to re-gap it. That way GM is made MORE aware of this issue.


I did - until GM tells the dealerships to do this it's considered a "tune up" and get charged to do it.


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## crzyfirefighter (Apr 19, 2012)

ok i'm reporting back on my regap... on a tank of 92 10%ethonal... i got 389 miles on my tank... and my mpg went up by 5.. so i'm going to say that regaping is a must and gets better mpg.. a big thank you goes out to whoever found this problem....


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## XtremeRevolution (Jan 19, 2012)

crzyfirefighter said:


> ok i'm reporting back on my regap... on a tank of 92 10%ethonal... i got 389 miles on my tank... and my mpg went up by 5.. so i'm going to say that regaping is a must and gets better mpg.. a big thank you goes out to whoever found this problem....


I can't take all the credit, but I'm glad you saw a significant difference. What were your original gaps, and which engine do you have?


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## jblackburn (Apr 14, 2012)

I did just from curiosity. 

To my pleasant surprise, response on Sunoco 87 is VERY MUCH improved, though I will probably still opt for higher octane in the summer. 

However, for temps where it's not really hot outside, it is now very tolerable on regular. Which is part of the reason I bought this car when my old turbo would only run well on 89-93. 


Sent from my Autoguide iPhone app


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> I did - until GM tells the dealerships to do this it's considered a "tune up" and get charged to do it.


Depends on the dealer I suppose. See this thread:

http://www.cruzetalk.com/forum/9-ch...sults-yesterdays-service-visit.html#post94704



The Wolf Wagon said:


> Took my 2012 Eco in for a service visit for a few items yesterday. Here are the issues and results:
> 
> 3) Check Spark Plug Gap. RESULT: FOUND GAP IN ALL SPARK PLUGS AT .030. REGAPPED TO GM SPECS .035 AND REINSTALLED.


Looks like his dealer did it for free...


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## XtremeRevolution (Jan 19, 2012)

jblackburn said:


> I did just from curiosity.
> 
> To my pleasant surprise, response on Sunoco 87 is VERY MUCH improved, though I will probably still opt for higher octane in the summer.
> 
> ...


I might just try it next tank of gas. Save me a couple of bucks. I'll be scanning for KR if I do. Do you have Torque?


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## jblackburn (Apr 14, 2012)

XtremeRevolution said:


> I might just try it next tank of gas. Save me a couple of bucks. I'll be scanning for KR if I do. Do you have Torque?


I have an iPhone. There's something called Rev, and I tried out a cheap adapter with my Volvo, but it wouldn't connect to the car. 

I'd be interested what you find out though. As you probably remember, that hesitation and lag was one of my major annoyances with my Cruze. 

I believe my gas mileage may have been a bit less (33-35 mpg for 200 miles @72-80 mph on a trip this weekend, AC on 3 the whole trip down and stuck in stop and go traffic for a while), but I don't drive consistently enough to notice if that's really less or not. 


Sent from my Autoguide iPhone app


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> Depends on the dealer I suppose. See this thread:
> 
> http://www.cruzetalk.com/forum/9-ch...sults-yesterdays-service-visit.html#post94704
> 
> Looks like his dealer did it for free...


He also had a check engine light on when he went in. I don't. What I was told specifically was that the dealership would need to justify pulling the plugs based on the owner's reported problem. A check engine light could be cause for this, especially if it was indicating a problem with the fuel/air ignition system. Then you could pull the plugs to ensure no carbon buildup or other problems with them. Even a "free" service has to be paid for somewhere. For warranty work the dealership has to "prove" to GM that the work was necessary. Misleading your dealership is never good for a long term service relationship.


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> He also had a check engine light on when he went in. I don't. What I was told specifically was that the dealership would need to justify pulling the plugs based on the owner's reported problem. A check engine light could be cause for this, especially if it was indicating a problem with the fuel/air ignition system. Then you could pull the plugs to ensure no carbon buildup or other problems with them. Even a "free" service has to be paid for somewhere. For warranty work the dealership has to "prove" to GM that the work was necessary. Misleading your dealership is never good for a long term service relationship.


Well that sucks. Looks like unless Stacy has recorded all of the information in this thread and forwarded it to GM, we're stuck having to do this on our own. Not that it's a big deal, but it's a bit irritating.


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## smorey78 (Apr 8, 2012)

Ok i am sitting on the fence with this one! what i know from past turbo cars i have owned is that the higher the boost the lower the spark plug gap. my supra had a .020 gap but was running 42psi. now gm put what $500 million into the cruze R&D...do you think they got the gap wrong...maybe maybe not. it does make me wonder why the owners book says .029 and SI, alldata state .035...i don't get that one! If you do a random search for boosted cars of all kinds...i mean all kinds...chevy, ford, srt-4, supercharged or turbocharge, vw and look for any of them having a "spark blow out problem" they have all reduced the gap to under .029. they all had that in common and all were running over 20psi! now as for a single engine have all 4 plugs gaped different...that's not right! so for the guys running a tune and over 20psi i might not gap to .035 for most of us running no tune and under 20psi .035 should be good! i just wonder if there is some thing deeper to all this!


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## XtremeRevolution (Jan 19, 2012)

smorey78 said:


> Ok i am sitting on the fence with this one! what i know from past turbo cars i have owned is that the higher the boost the lower the spark plug gap. my supra had a .020 gap but was running 42psi. now gm put what $500 million into the cruze R&D...do you think they got the gap wrong...maybe maybe not. it does make me wonder why the owners book says .029 and SI, alldata state .035...i don't get that one! If you do a random search for boosted cars of all kinds...i mean all kinds...chevy, ford, srt-4, supercharged or turbocharge, vw and look for any of them having a "spark blow out problem" they have all reduced the gap to under .029. they all had that in common and all were running over 20psi! now as for a single engine have all 4 plugs gaped different...that's not right! so for the guys running a tune and over 20psi i might not gap to .035 for most of us running no tune and under 20psi .035 should be good! i just wonder if there is some thing deeper to all this!


If you read this entire thread, much of this was already covered. If you're getting spark blowout, you can reduce your gap size. If not, the GM service manual is the authority on the subject, which advises .035. Set it to .035 and go on your merry way. I'm at .040 and no spark blowout issues to speak of. No tune either though. 

If you do have a tune, test it for yourself and see which works best.


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## silverram323 (Mar 16, 2012)

ECOmaniac said:


> Has anyone tried dropping back to a lower octane level after regapping? If detonation is causing performance issues at say 87, opening the plug gap up may remedy that issue - or make it worse depending on the source of ping..just thinking it may provide some cost savings and possibly even better performance. Just a thought.



Just my .02 here. 

I ran 87 octane for the 1st 2000 miles, never heard or felt any ping or knock in the engine. X recommended me to try 91 octane non OXY fuel ($.46 more per gal Here), so i did, two takes and 850 miles. I also think the engine is breaking in but i got 40.4 mpg on way to and from work. I regapped the plugs, and swapped back to 10% ethanol and 87 octane and my DIC it still showing the same MPG as my last two tanks with 91 octane. 

Here is a pic at 265 mile into the tank. 87 octane with 10% ethanol.


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> Well that sucks. Looks like unless Stacy has recorded all of the information in this thread and forwarded it to GM, we're stuck having to do this on our own. Not that it's a big deal, but it's a bit irritating.


Unfortunatly dealership service departments are stuck on this one. Unless you can demonstrate an issue that can impact the spark plugs they can't get GM to pay for the work. Now that my engine is broken in I'm going to step back to 87 octane and see if there is a drivability issue at 87. I'll use Shell for the testing.


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## crzyfirefighter (Apr 19, 2012)

XtremeRevolution said:


> I can't take all the credit, but I'm glad you saw a significant difference. What were your original gaps, and which engine do you have?



as my previous post i have the 1.4t and they were gaped at not even a .19 to .24


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## Vetterin (Mar 27, 2011)

obermd said:


> Unfortunatly dealership service departments are stuck on this one. Unless you can demonstrate an issue that can impact the spark plugs they can't get GM to pay for the work. Now that my engine is broken in I'm going to step back to 87 octane and see if there is a drivability issue at 87. I'll use Shell for the testing.


FYI, for the past 21,000 miles, 87 octane is all I have used in my car and yes, I can feel a difference in idle quality and low end torque after the regap (and I only gapped to .034).


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## obermd (Mar 3, 2012)

Vetterin said:


> FYI, for the past 21,000 miles, 87 octane is all I have used in my car and yes, I can feel a difference in idle quality and low end torque after the regap (and I only gapped to .034).


0.034 is in the margin of error 0.033 to 0.037.


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## mcg75 (Mar 5, 2012)

Guys, i asked Vince directly about this. He made a post on wot-forum. 

So... What exactly is the spark plug gap supposed to be on the 1.4 turbo?? - WOT-Tuning.com


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## obermd (Mar 3, 2012)

Interesting comments from Vince. I understand what he is saying about impacts on other parts of the engine. It appears we are in the unfortunate position of having to wait for GM engineering to get a definitive answer for the Cruze's 1.4T engine.


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## DMac1988 (Oct 3, 2011)

Hey, i regapped mine this morning. N noticed something awesome. The ride is smoother, more responsive. And for thise who have a auto and use the manual part, notice when ur stopping after 3rd gear the car knocks by dropping from whatever gear to 1st just to stop the car???....well mine does and after regapping just a lil i noticed the knock was almost gone. Its a lot less now. Im regapping again to remove all knocks and ill report back. And extreme, good job on the find. U may not want to take full credit but aleast take the credit for letting others know about something so stupid like this. My plugs where almost touching eachother. I used a ruler to measure the point to bend n saw it was 2mm away from it. Like fml!!! Im gonna respace to about .28 or if i can .30and then ill let u know tomorrow on a differnace on the knocking n so on.


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## XtremeRevolution (Jan 19, 2012)

mcg75 said:


> Guys, i asked Vince directly about this. He made a post on wot-forum.
> 
> So... What exactly is the spark plug gap supposed to be on the 1.4 turbo?? - WOT-Tuning.com


Saw it. And here's my response to him on facebook:



> Owner's manual also tells you the Auto trans holds 4 quarts. Tech specs say it holds 8 quarts. I dare you to drain it and put only 4 quarts back in.
> 
> BTW, I went through all 100 spark plug gaps recorded on CruzeTalk and made a bit of a breakdown. Your numbers certainly disagree with what people have reported there.
> 
> ...


One needs to keep in mind, this is his opinion based on general concepts. Generally speaking, once you widen the gap to a certain point, there will be additional stress on the coil. I personally don't think .035 is that point at which the coils get stressed unnecessarily. He thinks it is. Fair enough. Generally speaking, larger gaps can lead to spark blowout. That's correct, but I don't think .035 is that gap. Perhaps .050 will lead to spark blowout, or even .045, but not .040 (see the last 400 miles I've driven), or .035 (someone would definitely have reported it by now). 

He also thinks that the owner's manual is correct and the service manual is not. I'd beg to differ as I already pointed out in my transmission fluid capacity comparison that the owner's manual is not correct at least in one aspect and dangerously so. If someone changes their own transmission fluid and drains 6 quarts, do they put only 4 back in because the owner's manual says it only holds 4? One would assume that the service manual is more updated and current than the owner's manual.


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## obermd (Mar 3, 2012)

ECOmaniac said:


> This is kind of coming full circle now - the car should see full performance at 87 octane untuned - which would assume proper plug gapping. So those who bumped to 91 and got better performance would prob see the same results after the change based on what you are telling us.


This is why I'm going to switch back to 87 to document drivability issues.


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## vitgia78 (Mar 9, 2011)

My car uses NGK ZFR6U-11 with stock gap is 0.044" (1.1mm) - not 0.028" as Cruze in US (my car is Korean version). After regapping to 0.038" (0.95mm), I can feel a bit performance and throttle response. Thanks a lot.


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## Beaker (Mar 21, 2012)

DMac1988 said:


> Hey, i regapped mine this morning. N noticed something awesome. The ride is smoother, more responsive. And for thise who have a auto and use the manual part, notice when ur stopping after 3rd gear the car knocks by dropping from whatever gear to 1st just to stop the car???....well mine does and after regapping just a lil i noticed the knock was almost gone. Its a lot less now. Im regapping again to remove all knocks and ill report back. And extreme, good job on the find. U may not want to take full credit but aleast take the credit for letting others know about something so stupid like this. My plugs where almost touching eachother. I used a ruler to measure the point to bend n saw it was 2mm away from it. Like fml!!! Im gonna respace to about .28 or if i can .30and then ill let u know tomorrow on a differnace on the knocking n so on.


For the love of god please don't use a ruler to gap your plugs. Use a proper tool.


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## Skilz10179 (Mar 22, 2011)

Just read this whole thread, I still see no need to even check my plug gap...


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## garrettb1 (Feb 21, 2012)

A ruler, really? Maybe he works for NGK.:1poke:


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## XtremeRevolution (Jan 19, 2012)

Skilz10179 said:


> Just read this whole thread, I still see no need to even check my plug gap...


Mind = blown. Must not have actually read through the whole thread, or you're trying to troll me.

.019 - 2%
.020 - 11%
.021 - 0%
.022 - 4%
.023 - 3%
.024 - 27%
.025 - 33%
.026 - 8%
.027 - 2%
.028 - 6%
.029 - 4%

I'd laugh my ass off if you checked them and found one with a .020, one with a .024, one with a .028, and one with a .025 gap. 

No reason to check? Keep in mind, those numbers vary all over the place. People are getting huge variances between gaps in the same engine. It's not like person A had 4 plugs at .028, person B had 4 plugs at .025, and person C had 4 plugs at .021. 

If a a horrendous consistency isn't enough for you to take the 10 minutes to check the gaps to at least make sure they're all the same (never mind being correct), you must not care much about your car.

You'll spend a few hours installing an intercooler to get better performance but won't spend 10 minutes to check your spark plug gap when at least 25 less mechanically adept people on this board have, and measured the above variances. 

:question:


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## Skilz10179 (Mar 22, 2011)

I chose to believe they are gapped correctly within a certain tolerance from the factory, if they're a bit on the small side I'm cool with that.

Your comparison with the service manual about the trans fluid is pretty funny. You do know that when you drop the trans pan on automatic you don't lose all the fluid, multiple quarts will remain in the trans, mostly in torque converter and trans cooler. But I'm sure you knew that...


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## yukon (Aug 17, 2011)

XtremeRevolution said:


> Mind = blown. Must not have actually read through the whole thread, or you're trying to troll me.


Mind = Blown. On how much you actually care about a spark plug gap for your "Chevy Cruze".

Other's are entitled to thier opinion, so you dont have to keep throwing up meaningless percentages every time someone disagrees with you . Good Grief :th_thumbsdownsm:


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## XtremeRevolution (Jan 19, 2012)

Skilz10179 said:


> I chose to believe they are gapped correctly within a certain tolerance from the factory, if they're a bit on the small side I'm cool with that.
> 
> Your comparison with the service manual about the trans fluid is pretty funny. You do know that when you drop the trans pan on automatic you don't lose all the fluid, multiple quarts will remain in the trans, mostly in torque converter and trans cooler. But I'm sure you knew that...


Yes, I did know that. However, that information is entirely irrelevant and not funny. The manual specifically states:

*Capacities*
Metric English
Transmission Fluid
Automatic— 6 Speed 4.0 L 4.2 qt

That's *capacity*, not re-fill capacity once drained, but capacity. 

In my experience changing transmission fluid (4T60E and 4T65E), you typically lose 6-7 quarts of transmission fluid out of 8.5 quarts, usually due to the torque converter holding some, and other random places holding some as well. With the 4T80E, you typically lose 6 quarts as there's a section farther into the transmission that needs to be removed to drain the remaining fluid. Found this out when I worked on my Bonneville GXP. I've never drained a transmission of fluid and had only half of it come out. 

Are you suggesting that half of the fluid remains in the transmission when performing a drain? 

What would you define as an acceptable tolerance? So far, if we are to assume the spec is .028 (according to the manual) or .027 (according to NGK), the tolerance is so far off that it's not even funny. I can see .001-.002 as a possibly acceptable tolerance, but pushing into .003-.008 is a bit of a stretch. 

Here I've spent the last 24 pages helping people correct their spark plug gap, providing numbers, people posting testimonials about how big of a difference they make, and all the while I'm pushing to encourage people to check their spark plug gaps, citing reasons why it's important, and you come in and say "I still don't see any reason to check my spark plug gaps." 

I can read between the lines. Your comment can be rephrased as: "the last 24 pages of this thread are worthless, useless, and I see absolutely no merit to their existence."



yukon said:


> Mind = Blown. On how much you actually care about a spark plug gap for your "Chevy Cruze".
> 
> Other's are entitled to thier opinion, so you dont have to keep throwing up meaningless percentages every time someone disagrees with you . Good Grief :th_thumbsdownsm:


Oh, I'm sorry. Do we have another guy here who hasn't read the entire thread? Perhaps I should quote the number of users who fixed their severe bogging, hesitation, and lagging throttle issues with a spark plug gap correction. Or is that not relevant because you said so. God forbid we might actually care about our cars.

This is your first post on this forum? How interesting that my comment toward him specifically motivated you to "contribute" after 8 months of being on this board. Meaningless percentages? Mind backing up those statements? I and everyone else who have checked and gapped their plugs would hardly call them meaningless.


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## Skilz10179 (Mar 22, 2011)

I have no idea exactly how much fluid a torque converter in a Cruze holds and I don't really care either. I do know that some torque converters hold 4-5 quarts of fluid that will not drain during a basic trans servicing. The specs you posted earlier sounded exactly like service specs and not dry capacity.


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## XtremeRevolution (Jan 19, 2012)

Skilz10179 said:


> I have no idea exactly how much fluid a torque converter in a Cruze holds and I don't really care either. I do know that some torque converters hold 4-5 quarts of fluid that will not drain during a basic trans servicing. The specs you posted earlier sounded exactly like service specs and not dry capacity.


I'm waiting on GM customer service to call me back regarding a few issues I've contacted them to look into for me, two of them being the transmission fluid spec as well as the spark plug gap spec. The other being the issue people are having with the coolant smell. People deserve to know what PI is out for this, what the symptoms are, and deserve to be kept updated on this potentially hazardous issue. I'll take the issue up as far as it needs to go to get answers.

I'll report back on exactly why that is listed as 4 quarts. As a side note, I highly doubt this torque converter is large enough to hold 4 quarts of transmission fluid. If we were talking about heavier duty transmissions that require 12-14 quarts of transmission fluid, then I could understand 4 of those quarts being held up in the torque converter. I'd have a hard time believing that the torque converter in the Cruze is larger than that in a 4T65E or 4T80E. 

I'll find out either way.

One more thing to note. GM recently called for an increase in the spark plug gap spec for a late model Aveo due to emissions problems. I'll see if I can bring up that TSB.


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## XtremeRevolution (Jan 19, 2012)

yukon said:


> Congratulations, you were the reason for my first post! Too bad it was trying to defend others from your insolent replies.
> 
> I just checked out your profile and let me guess you’re in your mid 20's, have no job, and know everything. I have met several people like you in my life and there is no point in continuing a conversation with you. I am sure the mods would have banned you by now with the remarks you have made to others. That is if you didn't end up paying for your "Life Time Premium Membership." Good Luck with that.


So your second post is to insult me? That's your contribution after 8 months? Didn't help a single person, didn't offer advice to a single person, but you jumped right in to attack and insult me. 

I'm in my mid 20s, and I work full time as a Systems Security Administrator for a large health care company. I design sub boxes for free and build them for dirt cheap just to help pay for student loans and let me take my wife out to dinner a couple of nights a week. I also contribute more to this forum and go above and beyond to help more people (as plenty here will attest to) than you ever will with that attitude. 

Your first post was nothing but a direct attack against me. Who gave you the authority? When did I insult or attack you?


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## iKermit (Dec 13, 2010)

yukon said:


> Mind = Blown. On how much you actually care about a spark plug gap for your "Chevy Cruze".
> 
> Other's are entitled to thier opinion, so you dont have to keep throwing up meaningless percentages every time someone disagrees with you . Good Grief :th_thumbsdownsm:





yukon said:


> Congratulations, you were the reason for my first post! Too bad it was trying to defend others from your insolent replies.
> 
> I just checked out your profile and let me guess you’re in your mid 20's, have no job, and know everything. I have met several people like you in my life and there is no point in continuing a conversation with you. I am sure the mods would have banned you by now with the remarks you have made to others. That is if you didn't end up paying for your "Life Time Premium Membership." Good Luck with that.



What exactly are you trying to do? lol Run a revolution or something, because seriously, nobody will side with you here when it comes to him. Read the 20+ pages.


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## yukon (Aug 17, 2011)

iKermit said:


> What exactly are you trying to do? lol Run a revolution or something, because seriously, nobody will side with you here when it comes to him. Read the 20+ pages.


Spoken like a true sheep. But you are right. Since this is just a automotive forum I will bow down and step aside so we can get back to the topic at hand.


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## coinneach (Apr 10, 2012)

I've been internetting for a long time and BBSed for several years before that, and never have I seen so much animosity over such a simple issue. This topic is devolving into a religious war - on one side we have people, call them the Thomases, who heard a different version of the Word and had to find out for themselves; on the other we have those who believe the Word as handed down (in multiple conflicting versions, no less) and absolutely will not tolerate any dissent.

_They're just spark plugs, people._


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## cecaa850 (Apr 9, 2012)

XtremeRevolution said:


> One more thing to note. GM recently called for an increase in the spark plug gap spec for a late model Aveo due to emissions problems. I'll see if I can bring up that TSB.


They actually DEcreased the size of the gap from 1.0-1.1 mm to .9mm. OSB11-SM-085.


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## cecaa850 (Apr 9, 2012)

XtremeRevolution said:


> I'm waiting on GM customer service to call me back regarding a few issues I've contacted them to look into for me, two of them being the transmission fluid spec as well as the spark plug gap spec.


Auto trans holds 8.45 quarts.


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## XtremeRevolution (Jan 19, 2012)

Just called Chevy customer service and they put me on the line with a dealership. Per the service manual, the transmission in the Chevy Cruze drains exactly 5.8 quarts when removing the drain plug. Not 4 quarts (which is listed as the capacity in the manual). If you followed the manual assuming it showed a drain/refill capacity (which it doesn't explicitly state), you would be low 1.8 quarts on transmission fluid.

The dealership also confirmed that the correct spark plug gap for the 1.4L is .035"

The manual is wrong on both of these accounts. Currently on the phone with GM customer service finding out how this can be corrected in the owner's manual so they can have a new owner's manual shipped to me with the correct information free of charge.


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## Aeroscout977 (Nov 25, 2010)

A) Play nice here
B) Take it to the War Room
C) Use PMs

Easy choices to make =D


Also Vince makes a very compelling argument for the smaller gap. I'm including it as food for thought for people to mull over. Also thanks for posting the link!



Vince @ Trifecta said:


> An interest debate is going on these days - what is supposed the be the correct spark plug gap for the 1.4L turbo engine?
> 
> Well, if you believe the service manuals, it's .0335" - .037". But, my opinion is this is WRONG, and here's why:
> 
> ...


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## XtremeRevolution (Jan 19, 2012)

Aeroscout977 said:


> A) Play nice here
> B) Take it to the War Room
> C) Use PMs
> 
> ...


Noted.

I discussed his post on the facebook group. GM's customer service department openly admitted to me on the phone after we had finished speaking to the local dealership that the owner's manual is wrong and that two errors I've pointed out need to be corrected (spark plug gap and auto transmission capacity). Case number is 71-1068313756. 

Vince at this point is speaking only for himself and his own opinion in support of an error made in the owner's manual. I believe this is a much more compelling argument considering it's coming straight from GM.

Tuned vehicles are naturally excluded from this.

To respond to his post with regard to spark blowout, it will not occur in stock engines with the correct gap (.035). I've been running .040 for a while to push that limit and see at what point spark blowout does occur, and have not yet experienced issues. It may occur at .045 or .050, but I'm not at that point in testing yet. 

With regard to ignition coil failure, to rephrase him in light of GM's statements both from their customer support department and a local dealer, "If the gap is supposed to be .035", opening it to .042" (or any significantly larger gap than .035) may cause premature coil failure."


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## STUDLEE (Jul 6, 2011)

I can truely say this is the first time I have ever seen a group of people insult eachother on an online car forum then agree to move on for the sake of the topic. Thanks!

On the note of spark plug gap, before the Cruze, I owned an SRT-4 and I can say, from experience, that I have seen a night and day difference, in a 4cyl Turbo, a performance difference with even the most minute changes in plug gap. I have also seen the same "pickiness" when running copper vs platinum vs iridium (IDK what you guys say, iridium plugs CAN and DO need to be gapped) plugs. From my experience with 4cyl turbo cars (the SRT-4 and cruze not being the only ones) certain plugs and gaps can be all the difference in the world. In the neon with iridium plugs, I gapped .050 in my neon for best performance but they would wear out quicker vs the coppers that I ran at .035 that would be more stable and longer lasting. 

I say all this because I think the best Idea instead of arguing or talking to a chevy rep about it would be trial and error, with members posting their results. Copper, platinum, iridium, etc. I'd LOVE to see people post what worked best for them!


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## TechCruzer (Mar 15, 2012)

XtremeRevolution said:


> I'm in my mid 20s, and I work full time as a Systems Security Administrator for a large health care company. I design sub boxes for free and build them for dirt cheap just to help pay for student loans and let me take my wife out to dinner a couple of nights a week. I also contribute more to this forum and go above and beyond to help more people (as plenty here will attest to) than you ever will with that attitude.


Wow, but yet you write posts like you've been around a lot of cars & understand engineering well... I was guessing mid 30's (not trying to age you or anything). I personally have enjoyed reading your postings & the How-To's you've done & the time you take to do so. Thanks for that & helping out where you can & encourage you to keep it up.

Although it explains the Sub box stuff... in my early 40's so not my cup-o-tea.

On the subject at hand, please let us know more about what you find out regarding GM's manual mistakes & any further insight you get regarding the specs for our cars... I'm not comfortable doing my own engine work & will be taking my Cruze to the dealership to ask if they could check the plug gaps & verify they are to specs.

Thanks for your time... I know I appreciate it.


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## Hatje (Jun 23, 2011)

Yea I'm not gonna bother with this one next time I take it to the dealer I'll ask em to check that's what warrentys are for. 


Sent from my Autoguide iPhone app


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## H3LLON3ARTH (Dec 16, 2011)

TechCruzer said:


> Wow, but yet you write posts like you've been around a lot of cars & understand engineering well... I was guessing mid 30's (not trying to age you or anything). I personally have enjoyed reading your postings & the How-To's you've done & the time you take to do so. Thanks for that & helping out where you can & encourage you to keep it up.
> 
> Although it explains the Sub box stuff... in my early 40's so not my cup-o-tea.
> 
> ...


As do I we've hade our battles but after being on this forum longer I've seen his statements and opinions to be very good to go by and wouldn't want him to stop his trials on our (Brand New Cars) that no one really knows anything about unless your an engineer for gm.

Sent from my Droid


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## kevjam79 (Mar 18, 2011)

Ok... I want to start by *thanking* Xtreme for finding this issue. I have a limited amount of time everyday to research issues with respect to private life (house, car, etc.) due to my family and career. Because of this lack of time, anytime someone can find a solution that I would never expect, it is greatly appreciated! I would have never expected a vendor sourcing/mid-production engineering change to occur on such a tried-and-true platform. I thought I was on my way to a lemon........

Car: 2012 2LT 6MT (12,XXX miles)

Symptoms Prior to Spark Gap Change:

Hesitation "Fall on your Face" Acceleration when utilizing 1st and Reverse.
- This was happening to the point the car would die, stutter or shimmy on take-off. 

Began moving up octanes.... Maybe that would help. It didn't. Started at 87 and worked my way up to 93 (where I am at now).

Transferring from vacuum to boost would create stuttering, power loss, and uneven power delivery into boost.
- Knowing what I know now... The timing was being pulled to the point (possibly no further) that the engine could not function without detonation.

Detonation and knock would occur when rolling and allowing RPMs to drop below 2000 RPMs and not downshifting.
- With the gap change, this is not required anymore... I can run well below 1000RPMs before detonation occurs.

Engine Temps would average 220 to 225 F.


Gapping Completed:

All plugs were < 0.025.

Gapped plugs to 0.035.

1 week in-service.


After One-Week of Driving in 70-80F Temps w/ 93 Oct.:

Power delivery coming into boost and out of boost is smooth and aggressive.

Boost is no longer sudden/abrupt, but it is un-perceivable during acceleration. It is like going from the old Honda VTEC to the new buttery smooth twin lobe designs.

I can start on flat surface under idle throttle without any feathering of the clutch or accelerator. (Feathering occurred with every start before.)

Engine revs out faster and engine braking is more effective.

Engine Temps average 205 to 210 F.

Of course, I haven't dynoed the car but everyday it seems to gain power. At this point, I have notice no detonation without forcing it below 1000 RPMs.

Another issue is solved with this change.... I didn't think it would actually go away, but I no longer have (what I thought was) clutch judder at low RPMs. I am not sure if it was ever the clutch or just a power application issue. I have seen this in MT 3/4 Ton trucks before, running rudimentary EFI but never in a modern EFI. 

For auto trannies, I think the detonation issues are likely masked by the TCM working overtime with the ECM. An auto owner should see improvement in shifting and overall fuel economy. 

My MT car background for reference:

87 Chevy Spectrum 5MT
89 Chevy 3/4 Ton CK 4MT
91 Toyota Tercel 5MT
04 Acura RSX Type-S 6MT
05 Subaru Legacy GT 5MT
08 Subaru WRX STi 6MT 

If you haven't checked your plugs, *please do*. This will change the lifespan of the engine and with the right tools it only takes 20 mins.

Additional info.... My general manager checked his 2011 LS 6MT and the plugs were set at 0.022. He regapped and has seen similar improvements.

Thanks again.

Kevin


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## Campuscop2003 (Mar 5, 2011)

If this has been mentioned and I missed it I'm truly sorry, on the topic of the 1.8L, since 98% of this thread is about the 1.4. Is there any mistakes with this gap in the manual as well? Has anyone asked GM about the 1.8? My head is exploding trying to figure out why its .028. The Astra is .035, my old 07 Aveo (Different engine, similar size) was .039 - .043 inches. Has to be a mistake! Has to be! I have mine at .028 as the manual states and I am seriously thinking of going to .035. I have had a very slight improvement in power going from .022, .019 and so forth to all .028. Gas mileage sucks, but only because I tend to have a lead foot.


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## XtremeRevolution (Jan 19, 2012)

Campuscop2003 said:


> If this has been mentioned and I missed it I'm truly sorry, on the topic of the 1.8L, since 98% of this thread is about the 1.4. Is there any mistakes with this gap in the manual as well? Has anyone asked GM about the 1.8? My head is exploding trying to figure out why its .028. The Astra is .035, my old 07 Aveo (Different engine, similar size) was .039 - .043 inches. Has to be a mistake! Has to be! I have mine at .028 as the manual states and I am seriously thinking of going to .035. I have had a very slight improvement in power going from .022, .019 and so forth to all .028. Gas mileage sucks, but only because I tend to have a lead foot.


This is off the record, and is only my opinion. I think the 1.8L should also be .035, per the Astra's gap and it being the same engine to my knowledge. Several others also upped it to .035 and had great things to say about it. I'd give it a shot if I were you.


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## Chevyderek72 (May 16, 2011)

Just regapped my plugs to .035 tonight. All 4 plugs were right around .025, it was getting dark so I didn't both to get exact measurements. But if I remember correctly 2 were right at .025, one was slightly above it, and one was slightly below. I bought a tool that had the wire type, and also the thin metal strips in increments. It was easier for me to use the strips vs the wires so I used that, putting a .025 and .010 together to get my .035, and only using the .025 to test the stock gap.

I took a drive for a few minutes and a couple of miles and it seems to feel better. Top rpm's feel the same, but lower rpm's feel smoother and overall better. One example is when starting in first and shifting to second (manual trans) it transitions from very low rpm to 2000-2500rpm much better, smoother, and faster without the normal slight bog and hesitation. To me it is very slight, and not something that would make me think it was a whole new car like other people have seen, but definitely seems to be better. 

Thanks XtremeRevolution for finding this!


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## XtremeRevolution (Jan 19, 2012)

Just something worth noting here. We've had about 30 people now do this who have posted (and who knows how many more who haven't posted), and every single one of them came back and said that they felt a good improvement. Many came back and said they had a massive improvement and it changed their car completely for the better. All were gapped to at least .032. Not a single person came in and said they experienced negative side effects from this and had to gap back down. Not one. 

Not a single person came in and said they gapped to .028 per the manual and had a good experience or that it solved problems like the .035 gap did, whether its the 1.4T or the 1.8. In fact, given the reports of knocking with a smaller spark plug gap, I'd be much more afraid of long term engine damage with a .028 spark plug gap on the 1.4T due to constant knock at low RPMs than I would of premature coil failure, which was an over-generalized speculation at best. 

Still not a single issue running a .040 gap. I won't run any larger than .040 long term, but I will try .045 at some point in the future to see if I can induce some spark blowout to determine at which point that happens with the stock motor.


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## jblackburn (Apr 14, 2012)

There were reports of audible knock at lower gaps? Or just the engine pulling timing because it heard something?

I know you scan while driving pretty often - have you seen any improvement in low-RPM knocking with the increased gap and/or have you tried out a tank of 87 to see how it does with pulling timing?


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## XtremeRevolution (Jan 19, 2012)

jblackburn said:


> There were reports of audible knock at lower gaps? Or just the engine pulling timing because it heard something?
> 
> I know you scan while driving pretty often - have you seen any improvement in low-RPM knocking with the increased gap and/or have you tried out a tank of 87 to see how it does with pulling timing?


See post 245:


> Detonation and knock would occur when rolling and allowing RPMs to drop below 2000 RPMs and not downshifting.


I did not test prior to adjusting my gap. I also have not tried a tank of 87 octane. I'm still on the same tank I started .040 with, lol, and I still have another 250 miles to go. Current DIC fuel economy is at 47.2mpg with a 33mph average speed, which puts me at around 65-70% city driving. I expect to hit at least 44mpg at the pump when I fill up next time, and possibly break my current record of 44.7mpg. I'm very confident that personal record will be broken.


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## cecaa850 (Apr 9, 2012)

Xtreme, for your averages, I just checked mine with a set of feeler guages. From the factory: .022 .021 .022 .023. Now all at .035.


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## XtremeRevolution (Jan 19, 2012)

cecaa850 said:


> Xtreme, for your averages, I just checked mine with a set of feeler guages. From the factory: .022 .021 .022 .023. Now all at .035.


Pardon my memory, but did you have the 1.8 or 1.4T?


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## cecaa850 (Apr 9, 2012)

XtremeRevolution said:


> Pardon my memory, but did you have the 1.8 or 1.4T?


Your memory is fine, if you start memorizing what each username has, I'd say you've crossed the obsessive compulsive line! I have a 1.4 (should have mentioned that, sorry).


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## XtremeRevolution (Jan 19, 2012)

I've compiled a new list of originally measured plugs based on new information since the last one was created in various threads. Sample size is 112 plugs, or 28 owners. 

.019: 1.8%
.020: 9.8%
.021: 0.9%
.022: 5.4%
.023: 3.6%
.024: 25.0%
.025: 32.1%
.026: 9.8%
.027: 2.7%
.028: 5.4%
.029: 3.6%

Original list for comparison:


> .019 - 2%
> .020 - 11%
> .021 - 0%
> .022 - 4%
> ...


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## ErikBEggs (Aug 20, 2011)

I'll have the dealer look at mine next time in service.


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## 70AARCUDA (Nov 14, 2010)

...not nit-picking, but it looks like the 0.021" gap percentage should be *0.9%* rather than *0.09%


.019: 1.8%□□.020: 9.8%□□□□□□□□□□.021: 0.9%□.022: 5.4%□□□□□.023: 3.6%□□□□.024: 25.0%□□□□□□□□□□□□□□□□□□□□□□□□□.025: 32.1%□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□□.026: 9.8%□□□□□□□□□□.027: 2.7%□□□.028: 5.4%□□□□□.029: 3.6%□□□□
*


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## XtremeRevolution (Jan 19, 2012)

70AARCUDA said:


> ...not nit-picking, but it looks like the 0.021" gap percentage should be *0.9%* rather than *0.09%
> 
> 
> .019: 1.8%□□
> ...


My typo. Thanks for pointing that out.


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## 4piecekit (Mar 17, 2011)

Well, I've read through all 258 posts in this thread and can't see a reason why I wouldn't at least check my gaps. I have the 1.8 MT and wasn't sure what to gap them to. I'll buy the gap tool this weekend and gap to .035.


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## XtremeRevolution (Jan 19, 2012)

4piecekit said:


> Well, I've read through all 258 posts in this thread and can't see a reason why I wouldn't at least check my gaps. I have the 1.8 MT and wasn't sure what to gap them to. I'll buy the gap tool this weekend and gap to .035.


Please report back what your original gaps were.


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## OnlyTaurus (Mar 20, 2012)

I'm sad to report.. I'm getting random misfires under WOT(or close to it) with gaps at .035. Must be getting 'blow-out'. Nice find Xtreme, but I'm going to put mine back(or get new ones) tomorrow, my engine just does not like it. It may be fine with factory tunes, but the performance tunes should have small gaps anyways. Can't say I didnt try though lol.


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## XtremeRevolution (Jan 19, 2012)

OnlyTaurus said:


> I'm sad to report.. I'm getting random misfires under WOT(or close to it) with gaps at .035. Must be getting 'blow-out'. Nice find Xtreme, but I'm going to put mine back(or get new ones) tomorrow, my engine just does not like it. It may be fine with factory tunes, but the performance tunes should have small gaps anyways. Can't say I didnt try though lol.


Lol! I didn't even realize you had the Trifecta tune. Yeah, that would change everything. Since I don't have the tune, I have no way of knowing what works best under the higher boost pressures. The .035 is only valid for stock tuned motors. Cranking boost pressures changes everything. I mentioned this on the facebook group as well. 

No need to replace them though. Just make the gaps smaller. I'd try going down by .002 and see where your stop getting spark blowout. Maybe start at .032, then go to .030, and check if you still get spark blowout. Find the point at which no more blowout occurs, and leave it at that.


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## OnlyTaurus (Mar 20, 2012)

XtremeRevolution said:


> Lol! I didn't even realize you had the Trifecta tune. Yeah, that would change everything. Since I don't have the tune, I have no way of knowing what works best under the higher boost pressures. The .035 is only valid for stock tuned motors. Cranking boost pressures changes everything. I mentioned this on the facebook group as well.
> 
> No need to replace them though. Just make the gaps smaller. I'd try going down by .002 and see where your stop getting spark blowout. Maybe start at .032, then go to .030, and check if you still get spark blowout. Find the point at which no more blowout occurs, and leave it at that.


It's all good man. That's why we experiment!


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## Chevyderek72 (May 16, 2011)

Glad to say I am very happy with mine at .035 on the stock tune. Today I dropped my buddy off from carpooling and we talked for about 5 minutes and I left my car on. Got back in my car with the temp showing 100 outsite and intake at 170. Normally this result in the engine being a total dog and terrible till it cools down. This is also with the A/C on and fan speed on 2, but it actually felt great. I was shocked at how good it felt, much much better than normal.


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## obermd (Mar 3, 2012)

OnlyTaurus's experience may be why Vince is pushing for the 0.025 to 0.028 gap.


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> OnlyTaurus's experience may be why Vince is pushing for the 0.025 to 0.028 gap.


That's what I'm thinking. The .025 started since that's what was probably in the car he pulled them from. Boats mentioned it earlier in this thread. The .028 was in the manual. That's about to change. 

My personal hypthesis? I think tuned cars would run nicely without spark blowout at .030. I'd spend a tank of gas testing if I had the tune, lol.

Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


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## charlie_t (Nov 24, 2010)

I regapped my plugs about a week ago and it seems to me at low rpms my 2LT is a little more responsive. Like others, my gaps were in the .022 tp .024 range. Also the leftmost plug had a whisker extending from the center electrode. It hadn't bridged but it was about halfway there. That was scary. At some point I think it could have left me stranded. Thanks to all who have brought this to our attention.


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## Calintz (Jul 21, 2011)

Hey guys I just re-gapped my plugs

1 = 0.20 (Yeah I know)
2 = 0.25
3 = 0.22
4 = 0.27

Re-gapped them to 0.35 and like everyone said it runs a lot smoother a bit more pull as well. When I took off the top look what I saw.








THERE WAS A RUBBER PLUG TOP ON MY SPARK PLUG!!!!! I think i was running on three cylinders this whole time and please note that this was the first time I ever took off the top ever since I bought the car. I just shaked my head this is ridiculous but in any case my car feels smoother.


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## XtremeRevolution (Jan 19, 2012)

Calintz said:


> Hey guys I just re-gapped my plugs
> 
> 1 = 0.20 (Yeah I know)
> 2 = 0.25
> ...


Un-freakin believable. They left that in there? So much for quality control GM. Anyone who still thinks GM couldn't make a stupid mistake like this needs to look no further, lol. 

I'm glad your engine is running better now. Those .020 and .022 gaps were probably causing all sorts of issues. Glad you got that fixed! Well done.


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## sciphi (Aug 26, 2011)

OnlyTaurus said:


> I'm sad to report.. I'm getting random misfires under WOT(or close to it) with gaps at .035. Must be getting 'blow-out'. Nice find Xtreme, but I'm going to put mine back(or get new ones) tomorrow, my engine just does not like it. It may be fine with factory tunes, but the performance tunes should have small gaps anyways. Can't say I didnt try though lol.


I'm tuned and gapped my plugs to 0.030". Nothing but good results to say about it, even going WOT. No CEL's, no misfiring, just smooth power delivery and slightly better fuel economy. I was thinking about re-gapping to 0.035", but was too lazy to get off my duff and redo the plugs. Glad to hear that 0.035" is too big! 

And, that's incredible that a piece of rubber in the spark plug well wasn't caught at the engine plant. Amazing it wasn't causing more problems.


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## Swampassjr (Mar 25, 2012)

Calintz said:


> Hey guys I just re-gapped my plugs
> 
> 1 = 0.20 (Yeah I know)
> 2 = 0.25
> ...


If you were only running on 3 cylinders, you would've had a CEL this entire time


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## Ragin Cajun (Feb 11, 2012)

Just checked all mine. There were all less than .25. I regapped them to .30. Engine doesnt seem any different. I dont regularly drive this car but Ill check the mileage next time my wife fills it up. The plugs looked good though and really showed no wear. The car has 13k miles on it. BTW, its a 1.4 auto LTZ/RS.


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## XtremeRevolution (Jan 19, 2012)

Ragin Cajun said:


> Just checked all mine. There were all less than .25. I regapped them to .30. Engine doesnt seem any different. I dont regularly drive this car but Ill check the mileage next time my wife fills it up. The plugs looked good though and really showed no wear. The car has 13k miles on it. BTW, its a 1.4 auto LTZ/RS.


The difference is more noticeable with the manual trans as those who have them regularly run lower RPMs. The torque converter in the manual keeps RPMs constantly higher. It's also more noticeable at .035. 

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## kevjam79 (Mar 18, 2011)

sciphi said:


> I'm tuned and gapped my plugs to 0.030". Nothing but good results to say about it, even going WOT. No CEL's, no misfiring, just smooth power delivery and slightly better fuel economy. I was thinking about re-gapping to 0.035", but was too lazy to get off my duff and redo the plugs. Glad to hear that 0.035" is too big!
> 
> And, that's incredible that a piece of rubber in the spark plug well wasn't caught at the engine plant. Amazing it wasn't causing more problems.


This is the gap that I expected to be the best fit for the Trifecta Tunes. I am not sure of the changes in CFM for the up in pressure for the OEM turbo but with any application on a boost increase; you have to tweak the gap to match the CFM changes.


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## audiobahnman (Sep 2, 2011)

just re-gapped my 1.8L to .35
1= .25
2= .25
3= .22
4= .24
so far I've put a few miles on it, still seems to run just fine


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## ozman2005 (Apr 30, 2012)

Checked mine today. All four were right around .026. Opened them all to .035 and noticed an immediate difference in low RPM handling. I only drove it a couple miles after re-gapping but the engine was noticeably smoother from a stop. Can't wait to see how it does on the drive to work tomorrow. The car has just over 450 miles on it and is the 6MT.


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## sedanman (Dec 10, 2010)

Why do people keep writing 0.25? 0.25"? That's a quarter of an inch! Ya think you might be off by a factor of ten there sparky!?

It's 0.025"!


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## crazylegs (Apr 25, 2012)

I checked my plug gaps yesterday on my 2011 LTZ RS A6 and they were all at .024". I gapped them to .035" and it did run smoother but didn't notice a change in low rpm acceleration. Will be filling tank tomorrow to see if I can improve mpg from the current avg of 33.1. I also removed the air intake sleeve at the wheel well.


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## Aeroscout977 (Nov 25, 2010)

I think we need to give it time. The safe bet is to follow GM's guide lines. They hold your warranty in hand. Lets see if they release anything on the issue. Might be a good idea if someone PMs Stacy on the issue as well for possibly a community based follow up on the issue.


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## obermd (Mar 3, 2012)

Stacy has been monitoring this thread.


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## Patman (May 7, 2011)

OnlyTaurus said:


> It's all good man. That's why we experiment!



I have the 1.8 with the Trifecta Tune 6 M. Maybe it has something to do with the Turbo or the automatic, I have no problems! Seemed to improve my performance. All is well!


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## UpstateNYBill (Jan 14, 2012)

sciphi said:


> I flipped the switch to sport mode today and went blasting uphill. There wasn't a funny transition around 2200 RPM like I'm used to getting, and the car accelerated like a scalded cat, faster than I remember. I've blasted up this hill 2x/week for the past 3 months, both in sport and regular modes. The hill rises about 500 vertical feet over the course of a mile, so it's pretty darned steep. This was the first time I blasted up it with correctly-gapped plugs and sport mode engaged. It had no problem holding 4th on a section of hill that usually needs 3rd, even in sport mode. There was a noticeable difference, namely that it was quicker, smoother, and could hold a lower gear to go up a particularly steep section.


I've been testing a similar situation. I have a hill, where in sport mode, it could not hold the transmission in 6th gear in sport mode when the cruise was set to 62 at the bottom. It had to drop to 5th gear, as the speed had dropped below about 40 mph. This was with 87 octane gas. With 93 octane gas, it could hold it in 6th gear, but just barely. Since the re-gap, with 93 octane, it seems it can hold 6th gear with an increase of at least 5 mph more in speed than before. The DIC has been a bit more accurate in the last few fill-ups as well.


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## XtremeRevolution (Jan 19, 2012)

UpstateNYBill said:


> The DIC has been a bit more accurate in the last few fill-ups as well.


I've noticed this too!! I figured it was just me and didn't want to say anything as I couldn't prove it.


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## audiobahnman (Sep 2, 2011)

sedanman said:


> Why do people keep writing 0.25? 0.25"? That's a quarter of an inch! Ya think you might be off by a factor of ten there sparky!?
> 
> It's 0.025"!


ccasion14: Haha yeah I realize the plugs are at 25 thousandths of an inch. 
I was just following the previous format i guess.


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## rlw_1224 (Nov 1, 2011)

I checked my plugs over the weekend and all were about 0.025 and re-gaped to .035. One thing I did notice though is that plugs had a white-ish residue on the ends. Does this indicate that the engine is running either lean or rich? Or is this normal for these types of plugs? Only driven about 40 miles since re-gaping them but haven't noticed any performance or fuel mileage benefits yet.


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## jblackburn (Apr 14, 2012)

Like this?









Nah, that's normal.


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## rlw_1224 (Nov 1, 2011)

jblackburn said:


> Like this?
> 
> View attachment 5621
> 
> ...


Yep, exactly like that. Thanks!


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## XtremeRevolution (Jan 19, 2012)

I got a return call back from GM's customer support. The lady I spoke to acknowledged that there is a discrepancy between what the dealerships have on file and what's in the owner's manual. She said she's still doing research on why there is this discrepancy and will be calling me back tomorrow. She acknowledge that there is a problem with both the transmission capacity specification as well as the spark plug gap specification. 

I'll update more when I get the next phone call.


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## Macman (May 4, 2011)

anyone in south Texas interested in helping me gap mine? It should be back from the dealer friday night I hope.


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## UpstateNYBill (Jan 14, 2012)

Macman said:


> anyone in south Texas interested in helping me gap mine? It should be back from the dealer friday night I hope.


Sure! When can I expect the plane tickets? 

It's actually real easy. Between the write-up here, and videos on YouTube, it would be hard to do it wrong.


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## TechCruzer (Mar 15, 2012)

Macman said:


> anyone in south Texas interested in helping me gap mine? It should be back from the dealer friday night I hope.


I'm with you Macman... I took my Cruze by the dealership this morning on a whim (took the day off last minute), anyway I told the service writer about the discrepancy between the OM & what I've found out by "talking" with several other Cruze owners & that others found inconsistencies with the gaps (.020- .025, etc.) & that I would like them checked & upped to .030 - .035 if set too small.

I started out by telling him I have been experiencing some sluggish reaction times while making yields, protected left turns, etc. He said oh we've had afew other complaints from other customers with the same story. I mentioned the spark plug gap & that I would've checked it myself but that I'm not comfortable with DIY since I am just not inclined to do it. No problem he says, I'll have the tech do that for you.

I had two other issues I asked them to check into... after a few hours he returns with good news on the other two issues, one fixed, & other will be fixed, but that the tech & senior tech could not duplicate my concerns onthe sluggishness (I didn’t think so) & the senior tech took out another Cruze off the lot & both ran the same. I asked about the spark plug gap. We checked them & they are gapped per what GM states they should be. What is that I asked? I don't know, whatever the book says it should be. <sigh>.

So I don’t know if anything was changed or not with the spark plugs... I could not tell on the ride home of any changes to performance.


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## XtremeRevolution (Jan 19, 2012)

They didn't check, I can guarantee it. If there's no problem for them to duplicate on the spot, they won't have a reason to have a technician waste shop time to look at a problem based on what they'd assume to be an "inexperienced customer's opinion." 

Sounds like you might have to do this yourself, or find another dealer who won't lie to you. I would also have asked to speak to the tech directly, not the service adviser.


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## 70AARCUDA (Nov 14, 2010)

XtremeRevolution said:


> Sounds like you might have to do this yourself, or find another dealer who won't lie to you. I would also have asked to speak to the tech directly, not the service adviser.


...I got the same _"...numb/dumb speak..." _when I asked at my dealership: _"...oh, they're OK because we couldn't replicate the problem you described." _Nothing whatsoever was explicity stated as to whether even ONE plug had been pulled to check/verify what the gap was. Argh!

...and, people w_onder_ *why* I'm *not* a "happy-camper" GM-fan?!?!?


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## XtremeRevolution (Jan 19, 2012)

70AARCUDA said:


> ...I got the say _"...numb/dumb speak..." _when I asked at my dealership: _"...oh, they're OK because we couldn't replicate the problem you described." _Nothing whatsoever was explicity stated as to whether even ONE plug had been pulled to check/verify what the gap was. Argh!
> 
> ...and, people w_onder_ *why* I'm *not* a "happy-camper" GM-fan?!?!?


Hey, GM =/= GM dealerships.


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## 70AARCUDA (Nov 14, 2010)

XtremeRevolution said:


> Hey, GM =/= GM dealerships.


...true, but "mothership" GM _seemingly_ does nothing about their bad/poor dealerships, so they're guilty by "responsibilty" in my book, thus the GM "captain" can go *down* with his ship as far as I'm concerned (wink,wink).


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## rbtec (Feb 3, 2012)

GM needs to issue a TSB to check the gap. Without it, the dealerships will not be paid for the work. I was quoted $60 to check. 


Sent from my Autoguide iPhone app


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## TechCruzer (Mar 15, 2012)

rbtec said:


> GM needs to issue a TSB to check the gap. Without it, the dealerships will not be paid for the work. I was quoted $60 to check.


Well, the service writer didn't even suggest charging me to check the plug gaps (would have declined, anyway).... soooo have to agree on the TSB, but I suppose if they get enough customer complaints they will hopefully do something about it. Thanks to Xtreme he's got GM on speed dial on the subject & will hopefully rattle the cage enough to make them listen.


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## XtremeRevolution (Jan 19, 2012)

TechCruzer said:


> Well, the service writer didn't even suggest charging me to check the plug gaps (would have declined, anyway).... soooo have to agree on the TSB, but I suppose if they get enough customer complaints they will hopefully do something about it. Thanks to Xtreme he's got GM on speed dial on the subject & will hopefully rattle the cage enough to make them listen.


Oh, I'm not letting them budge on this one until they print me out a new manual with absolutely zero flaws. Hopefully that will at least raise a few eyebrows. I am calling them every afternoon asking for an update until they are sick of me. Whenever I'm done talking, I ask that they read off the notes and give me an expected callback time. 

Not my first time dealing with customer support. They'll know me by name before this is over.

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## Starks8 (Jul 20, 2011)

XtremeRevolution said:


> Oh, I'm not letting them budge on this one until they print me out a new manual with absolutely zero flaws. Hopefully that will at least raise a few eyebrows. I am calling them every afternoon asking for an update until they are sick of me. Whenever I'm done talking, I ask that they read off the notes and give me an expected callback time.
> 
> Not my first time dealing with customer support. They'll know me by name before this is over.
> 
> Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App



Haha, that's what I'm talking about!


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## rbtec (Feb 3, 2012)

TechCruzer said:


> Well, the service writer didn't even suggest charging me to check the plug gaps (would have declined, anyway).... soooo have to agree on the TSB, but I suppose if they get enough customer complaints they will hopefully do something about it. Thanks to Xtreme he's got GM on speed dial on the subject & will hopefully rattle the cage enough to make them listen.


I'm hoping for a TSB soon.


Sent from my Autoguide iPhone app


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## cecaa850 (Apr 9, 2012)

Macman said:


> anyone in south Texas interested in helping me gap mine? It should be back from the dealer friday night I hope.


I'm in S.E. TX, you can PM me. It takes about 10 minutes (cool motor). If you're close I'd be happy to do it for you.


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## Macman (May 4, 2011)

cecaa850 said:


> I'm in S.E. TX, you can PM me. It takes about 10 minutes (cool motor). If you're close I'd be happy to do it for you.


Thanks, I live in San Antonio. I might ask my brother to do it, he's used to working on cars.


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## cecaa850 (Apr 9, 2012)

Macman said:


> Thanks, I live in San Antonio. I might ask my brother to do it, he's used to working on cars.


I'm about 4-1/2 hours from you. Wouldn't be worth your trip.


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## Macman (May 4, 2011)

Thanks.


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## XtremeRevolution (Jan 19, 2012)

I called GM again. Didn't get a call back today from GM because apparently the person I've been working with (Portia) is out of the office today or is with another customer. I went over the details of the case again with another representative, but this time made sure to mention that people are having this issue and their dealerships are sending them away without actually checking the gaps. I mentioned that there is a study done on this (my percentage list as noted a couple of pages go), and that the spark plug gaps are significantly under-spec. 

The representative I spoke to said that Portia worked with one of my local dealers recently to verify that .0335-.0374 is the correct spark plug gap range according to the service manual and that the manual needs to be corrected.

Basically, nothing new. I'll be calling back at 4:00 central time tomorrow like I have been unless I get a call from them first.


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## Starks8 (Jul 20, 2011)

Good stuff man! Keep the fight alive!


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## XtremeRevolution (Jan 19, 2012)

I guess someone let her know that I called and that she was late on her call, because I got a call back at 5:00 Central. She proceeded to tell me that the dealership's service foreman spoke to her and gave her the correct specs, so I asked for a new printed manual with the correct specs because I paid for it. 

Apparently, they cannot do that, so I asked her to get me to someone who can. At this point I was starting to get a bit irritated. I was wondering how long it would take to hit a wall, and I hit it today. She had the audacity to tell me that I can get the service manual too and to tell me where, so I said, "sure, as long as you pay for it!." "Sir, I'm sorry but we cannot do that." She proceeded to tell me how the owner's manual is just for general information, not for specific things. I ridiculed that thought as the owner's manual does specifically include information for the service of this vehicle and it should be correct, because if I as a car owner do not want to pay $125 per hour to have the dealer work on my car, I have the right to work on it on my own and have the correct information provided to me. 

So I told her to escalate this to a case manager. "Sir, I'm sorry but we need a valid reason to escalate this case. We cannot just escalate." I proceeded to explain the situation, that I had been polite, kind, and even patient. I went out of my way to fix a problem with my car that I shouldn't have had to fix because my dealer would not have fixed it for me, and I bought a car and paid for it and the manual has now been proven to be in direct contradiction to the service manual. 

I told her straight up, you (GM) screwed up and you (GM) are going to fix this. So she said "hold on let me get a supervisor." She put me on hold, then came back 5 minutes later and told me the supervisor will do his/her own research and call me back tomorrow. I asked for an appointment time and said I'm not hanging up until I get one, and she said 2:00-4:00 PM Eastern time. If I don't receive a call by 4:05 Eastern time tomorrow, I'm calling them back.

I was wondering how long it would take before I hit a wall. Time to start climbing.


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## Aeroscout977 (Nov 25, 2010)

Anyway to refer them to Stacy so she can provide them with this thread, and the fact everyone has had issues and fixed said issues by correcting plug gap? Sorry for punctuation I'm in a hurry and on the phone!


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## TechCruzer (Mar 15, 2012)

XtremeRevolution said:


> I guess someone let her know that I called and that she was late on her call, because I got a call back at 5:00 Central. She proceeded to tell me that the dealership's service foreman spoke to her and gave her the correct specs, so I asked for a new printed manual with the correct specs because I paid for it.
> 
> Apparently, they cannot do that, so I asked her to get me to someone who can. At this point I was starting to get a bit irritated. I was wondering how long it would take to hit a wall, and I hit it today. She had the audacity to tell me that I can get the service manual too and to tell me where, so I said, "sure, as long as you pay for it!." "Sir, I'm sorry but we cannot do that." She proceeded to tell me how the owner's manual is just for general information, not for specific things. I ridiculed that thought as the owner's manual does specifically include information for the service of this vehicle and it should be correct, because if I as a car owner do not want to pay $125 per hour to have the dealer work on my car, I have the right to work on it on my own and have the correct information provided to me.
> 
> ...


You know we need more people in the world with smarts, patience, & a diplomatic approach like Xtreme has... considering he's already done his own re-gaping of his Cruze's plugs & could really careless if GM/Chevrolet did anything about getting this oversight corrected since he doesn't need the dealer to touch his vehicle. I've said it once & I'll say it again... Thank you XtremeRevolution for everything you've donated to helping us with our cars & unselfish participation on this forum.



Sent from my Galaxy Nexus using AutoGuide.Com Free App


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## 70AARCUDA (Nov 14, 2010)

...as a "compromise" solution, you might ask GM for a _"...corrected REPRINTED page(s)...", _containing the *new* "*correct*" information(s), so that you can insert it/them into your Owners Manual.


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## TechCruzer (Mar 15, 2012)

Aeroscout977 said:


> Anyway to refer them to Stacy so she can provide them with this thread, and the fact everyone has had issues and fixed said issues by correcting plug gap? Sorry for punctuation I'm in a hurry and on the phone!


Stacy is completely aware of this thread... I've PM'd her about it, but because it's not an officially recognized problem by GM/Chevrolet there's little she can provided/do on the subject... that said I hope she's provided some of data inconsistencies that everyone has contributed along the way.

Though I knew I probably wasn't going to get much out my dealership visit on the subject, yesterday. I've gotten them to log it as a customer concern, etc.



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## XtremeRevolution (Jan 19, 2012)

TechCruzer said:


> You know we need more people in the world with smarts, patience, & a diplomatic approach like Xtreme has... considering he's already done his own re-gaping of his Cruze's plugs & could really careless if GM/Chevrolet did anything about getting this oversight corrected since he doesn't need the dealer to touch his vehicle. I've said it once & I'll say it again... Thank you XtremeRevolution for everything you've donated to helping us with our cars & unselfish participation on this forum.
> 
> 
> 
> Sent from my Galaxy Nexus using AutoGuide.Com Free App


Thanks man, that's very much appreciated. You're quite welcome. I'm glad I've been able to help. 

Regarding the spark plug situation, I figure someone needs to take a stand.


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## wilde74k (May 14, 2012)

Just checked mine, they were at 0.025, changed to 0.035, might feel a small difference.
2012 ls 1.8 6mt


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## XtremeRevolution (Jan 19, 2012)

wilde74k said:


> Just checked mine, they were at 0.025, changed to 0.035, might feel a small difference.
> 2012 ls 1.8 6mt


Welcome to the forums!

Do report back with the results once you've had a chance to drive it.


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## Rosstude (Jul 8, 2011)

Hey all,
First post here, been lurking about 1 year now. Got a 2011 Echo MT/1.4. Read this post, got the bug to wrench on something Sunday night, and checked the plugs. All were quite even, all gaped at .027. I set them at .034. After 2 days commuting, I can say the flat spot/bog/lagging/what ever you want to call it, from fist to second, and 2nd to 3rd is almost completely gone. Low end throttle response seems better too. Its not a radical change, but I think there is a difference. I pushed it hard this afternoon, ran up to 5,000+rpm, and still runs the same as always up there. I love the car, now more than ever. Absolutely no problems to date at 11,000 miles.
Hats off to Chevy for producing this car, my first new car, and first Chevy since I sold the last in a long line of stovebolts a few years back.


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## XtremeRevolution (Jan 19, 2012)

Rosstude said:


> Hey all,
> First post here, been lurking about 1 year now. Got a 2011 Echo MT/1.4. Read this post, got the bug to wrench on something Sunday night, and checked the plugs. All were quite even, all gaped at .027. I set them at .034. After 2 days commuting, I can say the flat spot/bog/lagging/what ever you want to call it, from fist to second, and 2nd to 3rd is almost completely gone. Low end throttle response seems better too. Its not a radical change, but I think there is a difference. I pushed it hard this afternoon, ran up to 5,000+rpm, and still runs the same as always up there. I love the car, now more than ever. Absolutely no problems to date at 11,000 miles.
> Hats off to Chevy for producing this car, my first new car, and first Chevy since I sold the last in a long line of stovebolts a few years back.


Hey there! Welcome to the forums to you too! You should make an intro thread in the introduction section. 

I'm glad you checked your plugs and noticed a difference. Feel free to stick around.


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## garrettb1 (Feb 21, 2012)

Well the wife let me check the plugs in the cruze on Sunday. .023,.024,.025,.025 gaped to .035. She has never gotten more than 37mpg befor now. After 150 miles she is at 40mpg. I should be able to get 42-44 If I try. This car is an auto also.


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## Chevy Customer Care (Oct 29, 2011)

Aeroscout977 said:


> Anyway to refer them to Stacy so she can provide them with this thread, and the fact everyone has had issues and fixed said issues by correcting plug gap? Sorry for punctuation I'm in a hurry and on the phone!




Aeroscout977,
I do document all this information. I, as well as others, have made GM aware of this. I don't have information on how they are handling this at this time but as I get more information I will pass it along to you. Please feel free to contact me anytime.
Thank you,
Stacy Chevrolet Customer Service


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## Macman (May 4, 2011)

Once I get my car back, my brother will help me correct the gap on my spark plugs.


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## obermd (Mar 3, 2012)

I already have confirmed a drivability issue at 87 octane. From a less than 1/4 full tank, filling with Shell 87 Octane makes my car unable to maintain the posted 55 near the top of a hill on a major road I drive daily. This is in 5th gear as it's too steep for 6th gear. With 91 octane it has no problem. Time to go back to the dealership with a "drivability issue" using the owner's manual's recommended octane fuel from a Tier 1 gasoline. The dealership needed something to tell GM why they were pulling the spark plugs and checking them under warranty. It only took one drive up that particular hill to realize there is a problem on 87 octane.


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## XtremeRevolution (Jan 19, 2012)

Supervisor called me back and started telling me what she can't do. I kept thinking to myself, give me something that you actually can do. She kept saying how she can't get me the owner's manual as that is a different department that she can't get in touch with, and that if I want to get any information, I should call the dealer as the service manual will have the information I need. However, she would not specifically say that the owner's manual was wrong. I could tell that my persistence with that question was starting to get irritating as I could hear it in her voice. 

I pretty much told her, the manual says one thing, and if the spec is listed there, it better be correct. The service manual says another thing, so which one of these is right? Now keep in mind, I was told she was going to do her own research then call me back. I'm 100% sure she didn't do any research, and barely even read the original tech's notes, because apparently the notes that specifically state what the correct spark plug gap (per the service manual) and the correct transmission capacity should be weren't good enough. I told her I'm going to need something, even if it's a document or piece of paper from GM specifically stating what the correction should be so I can stick it in my manual, and she kept telling me she can't do that, so I got fed up and told her she's going to HAVE to do it because there is an error. 

She gave me a lot of "I cannot give you an answer on this" type of responses, clearly dodging my questions. She knows that I know that GM screwed up and is trying to downplay the scenario. 

She said she's going to do her own research and that I will get a call back on Friday between 2:00 and 4:00 PM. Again, I asked her for a specific time. I told her we will revisit the options as far as what needs to be done. 

Stacy, you are more than welcome to jump on this case if you want to save this poor supervisor the frustration I'm about to give her if she doesn't tell me the truth come Friday afternoon. Case number is: 71-1068313756. 

The service consultant assigned to this case is Portia. 

I have called Rachel (the district case specialist I worked with for the strut popping noise issue) regarding this matter and have also left her with this case number and my contact information. I have contacted her because I am not at all convinced that Portia or her supervisor will be in any position to help any of us with this issue.


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## XtremeRevolution (Jan 19, 2012)

I've created a new spreadsheet. Went back through the 3 threads that this has been mentioned in and copied down everyone's information including their usernames and their reported gaps. 

I've attached my spreadsheet, in which 36 cars have been reported.

Summary:

.019: 0.7%
.020: 4.2%
.021: 1.4%
.022: 4.2%
.023: 9.7%
.024: 18.1%
.025: 41.0%
.026: 9.7%
.027: 5.6%
.028: 2.1%
.029: 3.5%


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## 70AARCUDA (Nov 14, 2010)

...that works out to *84.1%* being *0.025"±0.002"* or, alternatively, _between:_ 0.023-*0.025*-0.027 inches, which imples 15.9% are out-of-spec either (a) from NGK or (b) banged up during GM installation?!?


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## Aeroscout977 (Nov 25, 2010)

Without printing new manuals for all owners GM could just send out an official amendment to be put with the owners manual then just update the new ones being sent out. I also have a feeling that the XMSN oil capacity may be correct. I feel that the owners manual accounts for the tranny itself. The shop manual most likely includes the torque converter capacity with it. An argument may be made that drain and servicing of the XMSN oil only requires X amount and not include the torque converter.


I'm not sure because I haven't seen the tech manual myself so everything I've stated above is a guess!


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## XtremeRevolution (Jan 19, 2012)

Aeroscout977 said:


> Without printing new manuals for all owners GM could just send out an official amendment to be put with the owners manual then just update the new ones being sent out. I also have a feeling that the XMSN oil capacity may be correct. I feel that the owners manual accounts for the tranny itself. The shop manual most likely includes the torque converter capacity with it. An argument may be made that drain and servicing of the XMSN oil only requires X amount and not include the torque converter.
> 
> 
> I'm not sure because I haven't seen the tech manual myself so everything I've stated above is a guess!


I already confirmed the above transmission capacity. The capacity is indeed 8.5 quarts, and 5.8 quarts are removed during a drain when the drain plug is removed. 

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## obermd (Mar 3, 2012)

70AARCUDA said:


> ...that works out to *84.1%* being *0.025"±0.002"* or, alternatively, _between:_ 0.023-*0.025*-0.027 inches, which imples 15.9% are out-of-spec either (a) from NGK or (b) banged up during GM installation?!?


This leads more support to my earlier observation that there may have been a typo in the spec sent to NGK. Instead of 0.035 GM sent over 0.025.


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> This leads more support to my earlier observation that there may have been a typo in the spec sent to NGK. Instead of 0.035 GM sent over 0.025.


Curiously enough, NGK claims they should be .027, although your theory does sound plausible.

The world may never know, lol. 

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## XtremeRevolution (Jan 19, 2012)

Update on this case. Stacy took ownership of it and has assigned it to a district case specialist. I received the private message regarding that today. She noted that I should be receiving a call back within 48 hours. 

Many thanks to Stacy and her involvement in this issue.


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## Skilz10179 (Mar 22, 2011)

XtremeRevolution said:


> Update on this case. Stacy took ownership of it and has assigned it to a district case specialist. I received the private message regarding that today. She noted that I should be receiving a call back within 48 hours.
> 
> Many thanks to Stacy and her involvement in this issue.


Good luck with that on a holiday weekend lol. But in all seriousness, I'm interested to see what they say.


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## XtremeRevolution (Jan 19, 2012)

Skilz10179 said:


> Good luck with that on a holiday weekend lol. But in all seriousness, I'm interested to see what they say.


Me too! The last two people I spoke to kept telling me nothing can be done. Maybe this spreadsheet I've made can help a little? Who knows. I will certainly report back as soon as I get more information or progress.


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## 70AARCUDA (Nov 14, 2010)

XtremeRevolution said:


> *Many thanks to Stacy *and her involvement in this issue.


...yes, indeed, "*Thank You*," Stacy ! ! ! !


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## XtremeRevolution (Jan 19, 2012)

This certainly gained traction much more quickly than I had expected. I received a call from the case specialist by the name of Mira, with whom I spoke for about 15 minutes explaining the details of the concerns I had. 

She was the first to tell me what can be done. She told me that should this correction need to be made, they can make the correction or at a bare minimum, make it available to dealers to print out a document for customers to place into their manuals as a correction. 

I explained that the biggest issue I have is that the dealerships are pushing customers away without checking their plugs because the problems associated with them cannot be reproduced. I argued that these are very circumstantial problems, relying on specific conditions such as air conditioning being on, heavy rush hour traffic with hot stagnant air, heavy heat soak in the engine and intercooler, and high outdoor temperature. Just because a customer cannot reproduce the issue on the spot, doesn't mean there isn't a problem. 

This person seemed much more helpful and implied that she can call on "resources" to look into this issue further. At this time, she has promised to do further research into the issue and will be calling me back on Wednesday from 2:15-4:15 PM Eastern time.


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## obermd (Mar 3, 2012)

obermd said:


> I already have confirmed a drivability issue at 87 octane. From a less than 1/4 full tank, filling with Shell 87 Octane makes my car unable to maintain the posted 55 near the top of a hill on a major road I drive daily. This is in 5th gear as it's too steep for 6th gear. With 91 octane it has no problem. Time to go back to the dealership with a "drivability issue" using the owner's manual's recommended octane fuel from a Tier 1 gasoline. The dealership needed something to tell GM why they were pulling the spark plugs and checking them under warranty. It only took one drive up that particular hill to realize there is a problem on 87 octane.


After 160 miles I gave up and switched back to 91 octane. My car is basically not safe to drive on 87 Octane. Shift points to get reasonable acceleration were anywhere from 1,000 to 2,000 RPM higher. Tank (DIC) MPG was 40.2 MPG. My previous 5,000 miles had averaged 42.0 MPG measured and the DIC had been reading 46 to 48 at refuel time. Air temps have been in the upper 60s to mid 70s during this test. 

At this refuel, I took advantage of the fact that I know I can get over 3 gallons into the tank after the first click-off in order to mix as much 91 octane in as I could, resulting in something over 88.5 octane mix. The car started driving better within 10 miles.

Next up will be checking and regapping the spark plugs. I'll probably check my son's 2012 LS that we just bought yesterday as well.


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> After 160 miles I gave up and switched back to 91 octane. My car is basically not safe to drive on 87 Octane. Shift points to get reasonable acceleration were anywhere from 1,000 to 2,000 RPM higher. Tank (DIC) MPG was 40.2 MPG. My previous 5,000 miles had averaged 42.0 MPG measured and the DIC had been reading 46 to 48 at refuel time. Air temps have been in the upper 60s to mid 70s during this test.
> 
> At this refuel, I took advantage of the fact that I know I can get over 3 gallons into the tank after the first click-off in order to mix as much 91 octane in as I could, resulting in something over 88.5 octane mix. The car started driving better within 10 miles.
> 
> Next up will be checking and regapping the spark plugs. I'll probably check my son's 2012 LS that we just bought yesterday as well.


Sounds great! Please remember to record the original gaps.


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> Sounds great! Please remember to record the original gaps.


I'll probably do this next weekend. I need to get a wire guage and want the car "cold" when I do it.


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> She was the first to tell me what can be done. She told me that should this correction need to be made, they can make the correction or at a bare minimum, make it available to dealers to print out a document for customers to place into their manuals as a correction.


I'm not so worried about the information in the printed owner's manual that came with the car - specs do change. A corrected on-line manual would really be nice.



XtremeRevolution said:


> I explained that the biggest issue I have is that the dealerships are pushing customers away without checking their plugs because the problems associated with them cannot be reproduced. I argued that these are very circumstantial problems, relying on specific conditions such as air conditioning being on, heavy rush hour traffic with hot stagnant air, heavy heat soak in the engine and intercooler, and high outdoor temperature. Just because a customer cannot reproduce the issue on the spot, doesn't mean there isn't a problem.


Indeed... I talked to the service manager (not advisor) and salesman (who has sold me two Cruzen now) at my dealership yesterday while my car was having a paint gouge removed (something fell on it going in or out of the trunk). I explained that on 91 octane the car runs like a charm but on 87 octane (both from the same Shell station) the car has no power at low RPMs, feels the same at high RPM, requires shifting at higher RPM, gets lower MPG overall, and has knock that can be felt in the gas pedal but not heard or felt in the seat itself. I may have found the only way to quantify this problem - MPG. At least for the ECO MT the MPG hit is very measurable. His general response was that this is so out of the ordinary that he didn't know what to say. He said this actually runs counter to what you would expect because higher octane gas has less energy content, but that the anti-knock features of the car may be masking the issue.

GM simply needs to send out a TSB to their dealerships that say to check and correct spark plug gaps on all Cruzen that are in for any service that will allow the engine to cool down enough to safely do this work. Don't wait for the customer to complain - just do it. Even if there isn't a complaint, this will improve customer satisfaction with the car simply because the car will drive better.

I also wonder what the plug gaps were on the ECO MT that was GM/EPA tested? If they were off it could have lowered the EPA test results. A check of Fuelly shows that ECO MT owners are almost all getting significantly better MPG than the EPA results.


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## TechCruzer (Mar 15, 2012)

Well, I caved in & went to the auto store & bought a 6" ratchet extension, T-30 Torx bit, & spark plug 5/8 socket with the special neoprene insert to help hold the plug in after removal.

2012 ECO A/T Mfg. 11/11

I don't know the plug order, but left to right... 0.020, 0.025, 0.025, 0.020 are all now gapped to 0.035 & drove it around for about 15 miles & there is a 70% + improvement. As well as the yield & protected turns I was having the bog down, sluggish responses are way better now.

Thanks to everyone for pointing out how simple a task this was... I think everyone who has any complaint about the sluggishness, poor throttle response, hesitation do this adjustment. You will be much happier!


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## wallbngr (Feb 2, 2012)

XtremeRevolution said:


> Me too! The last two people I spoke to kept telling me nothing can be done. Maybe this spreadsheet I've made can help a little? Who knows. I will certainly report back as soon as I get more information or progress.


I just finnished regapping my plugs .. They are all now .035 ... 3 were set at .026 and one was .025


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## C5Shark (May 25, 2012)

Checked two cars.

2012 Eco automatic @~2700 miles - Stock were all around .025" +/- .001". Reset to .037". Did this about 2 weeks ago, no issues thus far.

2012 LS manual @1000 miles - Stock were all .025". I just finished resetting them all to .035". If no issues, I'm going to try .040".


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## Calintz (Jul 21, 2011)

C5Shark said:


> Checked two cars.
> 
> 2012 Eco automatic @~2700 miles - Stock were all around .025" +/- .001". Reset to .037". Did this about 2 weeks ago, no issues thus far.
> 
> 2012 LS manual @1000 miles - Stock were all .025". I just finished resetting them all to .035". If no issues, I'm going to try .040".



Sounds good man let us know how that goes on your LS. I was thinking of doing that to for my 1.8L as well. I have had no issues on mines since i gapped them to .035 I'm sure you wouldn't either but in any case I will try to gap them to .040 to see what happens.


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## obermd (Mar 3, 2012)

Regap results -

I started at 2 x 0.023" and 2 x 0.025". Regapped all to 0.035-0.036".

As a result of regapping, I can shift about 200 RPM lower and maintain a higher gear when going up hills - this is observed behavior of the car. In addition, my ECO feels like it starts slightly faster, but that may be psychological. I haven't tried high RPMs yet, but I suspect the impact of the turbo will overwhelm any gains from regapping. The engine is definitely smoother.

Shift old new
1-2 2300 2000
2-3 2300 2300 The jump to 3rd is just too much for a lower shift point and forces the engine speed too low
3-4 2000 1800
4-5 2000 1700
5-6 2000 1800

The lower shift points also translate into less "turbo lag" as a result of shifting simply because I'm not using the turbo as much.

In addition, the car doesn't shiver nearly as much when attempting to accelerate from idle RPMs and actually appears happy on level road at 1000 RPM, whearas before the regap I had to be at 1200 RPM for level road cruising.

To the moderators, please let XtremeRevolution add regapping on the 1.4T engine as a fuel efficiency item in the mechanical area. For 1.4T manuals the fact that we can run the car at lower RPM will definitely improve MPG.

I haven't had a chance to test 87 octane yet - I'm still on my mixed ~88.5 octane that I created prior to regapping.


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## XtremeRevolution (Jan 19, 2012)

Calintz said:


> Sounds good man let us know how that goes on your LS. I was thinking of doing that to for my 1.8L as well. I have had no issues on mines since i gapped them to .035 I'm sure you wouldn't either but in any case I will try to gap them to .040 to see what happens.


I ran .040 for about 3 tanks of gas and I didn't see any improvements over .035. I went back down to .036 on Monday. That said, this is a different motor, so your experiences will likely be different. Let us know what the results are!


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## wallbngr (Feb 2, 2012)

I regapped mine to .035 and The low end performance has improved ... Usrd to lag when I started from a stop ..
I'm going to see what a tank of 91 will do ..


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## XtremeRevolution (Jan 19, 2012)

Got the call back from GM today as promised. However, the representative did not do the research for me as promised. Instead, she told me that the GM Quality Assurance center has been notified of this issue and they are investigating the problem to determine a course of action. Basically, that's where the roads ends for me. They cannot provide me with updates (rather, will not, as I'm sure they *can*) and in the event that an update to the manual is deemed to be necessary, they will send out a letter to all Cruze owners and update the manual online. She declined to see the spreadsheet I've been putting together with the numbers provided by members of this board, and I had a strong impression that she was barely listening half the time I was talking, perhaps thinking she's not going to do anything anyway except for repeat the same things she did when she first called me back. 

However, I did not consider this to be an acceptable way to end this case, so I sent Stacy another private message. I need to know, officially from GM, what the correct spark plug gap is for this vehicle, and I want to see a TSB created. I don't want to be shoved aside and told "we have another team looking into it." GM district case managers should be more than just liaisons between customers and their dealerships. 

She further stated that anyone else who calls in to ask about this issue will have to jump through the same hoops as I did to get to this, but I disagree, as I do have her direct extension. You guys are more than welcome to call her direct extension and request the same information as I did, expressing the same concerns as I did. I'm sure she'll appreciate all of the voice mails. Putting some pressure on her will hopefully get her to put more pressure on that quality assurance department she mentioned to get this done ASAP. Her direct number and my case number are listed below:

Mira
Direct line: 866-790-5600 x31313
71-1068313756

As for me, I will be paying my local dealership a visit to have them look into this personally and get me _*something *_in writing on behalf of GM stating the correct specifications for this vehicle. 

I will report back what I hear from Stacy.


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## 70AARCUDA (Nov 14, 2010)

...sorry to see your efforts come to nothing (so far), as I know that you're doing the right thing, regardless of Global-GM's lip-serviced feet-dragging!

...it's come full circle, around again, to the point I made in my first post on this subject:



70AARCUDA said:


> ...ah, but the "real" question should be: _"...what does *GM* specify the gap *should* be?"_


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## Bohdan (Apr 28, 2012)

Perhaps GM will make the new plug adjustment to the 2013 Models along with there Manuals and just leave the 2011 to 2012 as is. They may have already realized that if they make it known to all then thousands of owners will be demanding money back for there loss of MPGs over the year.
I have spoken to quite a few owners of 2011 and 2012 and they are very happy with there MPGs so perhaps GM will just leave well enought alone.
I will be picking up my Cruze this weekend and will see if there was a change to the manual as to the plug gap.


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## XtremeRevolution (Jan 19, 2012)

Bohdan said:


> Perhaps GM will make the new plug adjustment to the 2013 Models along with there Manuals and just leave the 2011 to 2012 as is. They may have already realized that if they make it known to all then thousands of owners will be demanding money back for there loss of MPGs over the year.
> I have spoken to quite a few owners of 2011 and 2012 and they are very happy with there MPGs so perhaps GM will just leave well enought alone.
> I will be picking up my Cruze this weekend and will see if there was a change to the manual as to the plug gap.


The manual provided online has not yet been updated, so I am doubtful that you will have a newer version than the rest of us do. That said, I would highly recommend that you add "check spark plug gap" to the terms of your sale prior to driving off with the vehicle. That might be the only way you'll get them to do the job for you.




70AARCUDA said:


> ...sorry to see your efforts come to nothing (so far), as I know that you're doing the right thing, regardless of Global-GM's lip-serviced feet-dragging!
> 
> ...it's come full circle, around again, to the point I made in my first post on this subject:



The official "side-stepped" statement from GM with regard to what the correct gap should be is whatever the dealer's service manual says. I don't personally consider it a valid answer. I am under the impression that they will neglect to answer the question for liability reasons and will instead repeatedly forward you to your dealership.


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## obermd (Mar 3, 2012)

GM has more than a "legal" issue with this. There is a potential media problem. If GM issues a TSB to their dealerships to quietly fix the gapping as Cruzen come in for other service and the media finds out, the media will show its true colors as vultures.


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> GM has more than a "legal" issue with this. There is a potential media problem. If GM issues a TSB to their dealerships to quietly fix the gapping as Cruzen come in for other service and the media finds out, the media will show its true colors as vultures.


Perhaps my local media would like to hear more about this story. 100% of Cruzes have shipped with incorrect spark plug gaps and GM has refused to so much as admit what the correct gap issupposed to be.

I'll give Stacy a chance to redeem GM before resorting to media contacts.

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## Starks8 (Jul 20, 2011)

XtremeRevolution said:


> Perhaps my local media would like to hear more about this story. 100% of Cruzes have shipped with incorrect spark plug gaps and GM has refused to so much as admit what the correct gap issupposed to be.
> 
> I'll give Stacy a chance to redeem GM before resorting to media contacts.
> 
> Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App



HAHA, Love it man! Power to the people!!


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## UpstateNYBill (Jan 14, 2012)

XtremeRevolution said:


> Perhaps my local media would like to hear more about this story. 100% of Cruzes have shipped with incorrect spark plug gaps and GM has refused to so much as admit what the correct gap issupposed to be.
> 
> I'll give Stacy a chance to redeem GM before resorting to media contacts.


GM would do well to resolve this quickly. Many a dealership, and manufacturer, has learned the lesson too slowly and borne the wrath of the internet via car forums and social media. Trying to sidestep an issue, or bury it, can very easily blow up in their face.


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## sedanman (Dec 10, 2010)

I didn't believe it till I saw it with my own eyes. But one of my plugs was 0.022". I regapped them all to 0.034". I said I wouldn't go past the 0.028" in the Owner's manual but this thread and all the posters convinced me. Thanks XtremeRevolution for bringing this to our attention, making GM aware of it, and also for the resonator delete which improved throttle response on my stock tune 2LT. Sorry I doubted you, but in my years of doing tune ups I have never seen plugs so out of spec. from a plug manufacturer.


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## obermd (Mar 3, 2012)

UpstateNYBill said:


> GM would do well to resolve this quickly. Many a dealership, and manufacturer, has learned the lesson too slowly and borne the wrath of the internet via car forums and social media. Trying to sidestep an issue, or bury it, can very easily blow up in their face.


Agreed. So far there have only been 50 or so Cruzes with measured gaps that are out of spec, but if the media starts investigating they will randomly check Cruzes and the numbers could really add up fast and cost GM huge amounts in lost consumer confidence and possibly future sales. My personal belief is that this is nothing more than an simple typographical error in the spec sent to NGK and it would be easy and relatively inexpensive to fix, especially if done while the car is in for another reason. GM already has the ability to track corrective actions for recalls. This same "machinery" can be used to track which Cruzes have been checked and corrected. The customer goodwill generated by doing this will provide far more benefit that the cost of making the adjustments.


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## sedanman (Dec 10, 2010)

obermd said:


> Agreed. So far there have only been 50 or so Cruzes with measured gaps that are out of spec, but if the media starts investigating they will randomly check Cruzes and the numbers could really add up fast and cost GM huge amounts in lost consumer confidence and possibly future sales. *My personal belief is that this is nothing more than an simple typographical error in the spec sent to NGK* and it would be easy and relatively inexpensive to fix, especially if done while the car is in for another reason. GM already has the ability to track corrective actions for recalls. This same "machinery" can be used to track which Cruzes have been checked and corrected. The customer goodwill generated by doing this will provide far more benefit that the cost of making the adjustments.


I think there is more to it than just a typo. NGK says the spec is 0.028". They set them to 0.027". Yet people found gaps as low as 0.019". That leads me to believe there is either poor quality control or the plugs were damaged and gaps narrowed possibly by hitting them on installation or banged up in transit in shipping or in a storage bin if they were just loosely thrown into a barrel. I'm just speculating how this could happen because I have never seen this before. But it doesn't seem like a typo. A typo would not account for 0.019" if it's supposed to be 0.028" or 0.035"


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## obermd (Mar 3, 2012)

sedanman said:


> I think there is more to it than just a typo. NGK says the spec is 0.028". They set them to 0.027". Yet people found gaps as low as 0.019". That leads me to believe there is either poor quality control or the plugs were damaged and gaps narrowed possibly by hitting them on installation or banged up in transit in shipping or in a storage bin if they were just loosely thrown into a barrel. I'm just speculating how this could happen because I have never seen this before. But it doesn't seem like a typo. A typo would not account for 0.019" if it's supposed to be 0.028" or 0.035"


Since 90% of the plugs measured so far are between 0.023 and 0.027 with a huge peak at 0.025, I think GM sent 0.025 to NGK for both cars. Take a look at the graph I posted in the thread for reporting plug gaps and it becomes really obvious why I think this. I derived the graph from the first 42 cars reported on XtremeRevolution's spreadsheet. The additional cars that have been reported have intensified the peak at 0.025. Given that there are a significant number of outliers from this range, I definitely agree that there is a quality control issue either at NGK or at Lordstown, however. Lordstown needs to be randomly checking spark plugs before inserting them in the cars. We have also had a report that GM Global Connect specs 0.035 for the 1.4T engine and 0.028 for the 1.8 engine. Most of the cars represented in Xtreme's spreadsheet are 1.4T. Not a single plug reported so far has had a gap larger than 0.030, which is the upper edge of the 1.8 engine's gap specification. NGK also isn't being fully forthcoming with the few people who have contacted them directly, which doesn't surprise me - NGK's contract is with GM, not the car buyer.

Here's the current graph from Xtreme's spreadsheet.









With 196 spark plugs there is enough confidence that unless the underlying issue has been resolved that the basic shape and position of the peak shown in this graph will not change.


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## XtremeRevolution (Jan 19, 2012)

My updates today to the spreadsheet will confirm what obermd said. Most of them were in the ~.025 range. 49 cars counted so far, and one new report in this thread that I'll add tomorrow. 

I'd safely say someone thought they were supposed to be .025.


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## silverls (Nov 12, 2011)

coinneach said:


> Beg to differ. You can certainly use a 27, but 40 is more snug and doesn't slop around like a 27 or 30. Yes, even on the drums.


T40 didn't fit. Used a T30 and it was perfect.


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## XtremeRevolution (Jan 19, 2012)

silverls said:


> T40 didn't fit. Used a T30 and it was perfect.


Awesome. Thanks for clarifying that. The T27 worked but I could tell something a tad bit larger would fit, but didn't have one.


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## gman19 (Apr 5, 2011)

XtremeRevolution said:


> As for me, I will be paying my local dealership a visit to have them look into this personally and get me _*something *_in writing on behalf of *GM stating the correct specifications for this vehicle.
> *


FWIW...I dropped into my dealership yesterday. I think another poster already did this, and if so this will just back that post up.
The tech (NOT the service advisor), looked up and stated to me (from his reference) that the correct gap for the 1.4L Turbo Cruze is 0.033"-0.035".

That's all I inquired about was the gap. Didn't mention anything else, I figured the only way to get a straight up answer was to ask a straight up question.
I'll be checking mine whenever I get a cool engine opportunity, probably this weekend.


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## 98sonoma (Nov 30, 2010)

If you look at this AC Delco Document (from Australia), you'll see the gap is stated to be .9 for the 1.4l Turbo 






.9 millimeters = 0.0354330709 inches

I made this change and have noticed a little better fuel economy as well.


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> Awesome. Thanks for clarifying that. The T27 worked but I could tell something a tad bit larger would fit, but didn't have one.


I was actually able to use a T25, but it was iffy. If my torque screws had been any tighter I would have needed a T27.


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## obermd (Mar 3, 2012)

98sonoma said:


> If you look at this AC Delco Document (from Australia), you'll see the gap is stated to be .9 for the 1.4l Turbo
> View attachment 5895
> .9 millimeters = 0.0354330709 inches
> 
> I made this change and have noticed a little better fuel economy as well.


According to this document, the 1.8 should be gapped at 0.0315" (0.8 mm). Now I can regap my son's LS.


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## XtremeRevolution (Jan 19, 2012)

sedanman said:


> I didn't believe it till I saw it with my own eyes. But one of my plugs was 0.022". I regapped them all to 0.034". I said I wouldn't go past the 0.028" in the Owner's manual but this thread and all the posters convinced me. Thanks XtremeRevolution for bringing this to our attention, making GM aware of it, and also for the resonator delete which improved throttle response on my stock tune 2LT. Sorry I doubted you, but in my years of doing tune ups I have never seen plugs so out of spec. from a plug manufacturer.


Do you recall what the rest of them were gapped to aside from the .022 plug?


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## obermd (Mar 3, 2012)

sedanman said:


> in my years of doing tune ups I have never seen plugs so out of spec. from a plug manufacturer.


This is also why dealership service advisors and managers are shocked when asked about this.


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## obermd (Mar 3, 2012)

Anyone regapped a 1.8 yet? If so, what's the torque bit size needed? The 1.4 needs the T27.


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## rbtec (Feb 3, 2012)

obermd said:


> This is also why dealership service advisors and managers are shocked when asked about this.


I assume that the Sonics would be having the same issue.


Sent from my Autoguide iPhone app


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> Anyone regapped a 1.8 yet? If so, what's the torque bit size needed? The 1.4 needs the T27.


Several people on this board have. I believe it's the same assembly, but don't quote me on that.


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## TechCruzer (Mar 15, 2012)

obermd said:


> Anyone regapped a 1.8 yet? If so, what's the torque bit size needed? The 1.4 needs the T27.


Actually the T-30 is an exact fit for the spark plug assembly. T-27 is spot on for the brake drums.



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## zippy (May 16, 2012)

I got to my plugs the other day. 1-4 were all .025". I bent one electrode and had to put a new set in. GM ac delco 41-117 are the stockers. BUT, They were 2-3 days out. I had to put in autolite 3923X's, which were built a little better IMPO. I wanted to add, if you run 87 octane, you will decrease your MPG!! I did by 2-3 MPG. I ran the old plugs gapped to .035" for a day till I could get over to the parts store, and with 87, they were both getting me ~31-32MPG. With a .025" gap and 87 I got ~34-35MPG. It may have not made any differance on the bent electrode, but I wanted to make sure I had good plugs in it. I have a set of NGK ordered. If you run 89 or higher you are fine, just a heads up.


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## zippy (May 16, 2012)

reason for the decrease is that with a larger gap, it will cause it to have more knock due to the larger spark and more complete burn. You will need a fuel that is harder to burn to keep from knock. knock decreases spark timing, and timing advance is power, and without power the motor lags, and when it lags it uses more fuel. That is my logic anyhow.


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## XtremeRevolution (Jan 19, 2012)

zippy said:


> I got to my plugs the other day. 1-4 were all .025". I bent one electrode and had to put a new set in. GM ac delco 41-117 are the stockers. BUT, They were 2-3 days out. I had to put in autolite 3923X's, which were built a little better IMPO. I wanted to add, if you run 87 octane, you will decrease your MPG!! I did by 2-3 MPG. I ran the old plugs gapped to .035" for a day till I could get over to the parts store, and with 87, they were both getting me ~31-32MPG. With a .025" gap and 87 I got ~34-35MPG. It may have not made any differance on the bent electrode, but I wanted to make sure I had good plugs in it. I have a set of NGK ordered. If you run 89 or higher you are fine, just a heads up.


Did you run a full tank to notice that 2-3mpg loss?


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## XtremeRevolution (Jan 19, 2012)

zippy said:


> reason for the decrease is that with a larger gap, it will cause it to have more knock due to the larger spark and more complete burn. You will need a fuel that is harder to burn to keep from knock. knock decreases spark timing, and timing advance is power, and without power the motor lags, and when it lags it uses more fuel. That is my logic anyhow.


I've been scanning with Torque almost daily. Absolutely zero KR unless you're really lugging it at low RPMs.


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## sedanman (Dec 10, 2010)

XtremeRevolution said:


> Do you recall what the rest of them were gapped to aside from the .022 plug?


They were all close to 0.025" except that one. So I think it was 0.022", 0.025", 0.025", 0.026"

Not one of them even hit 0.027" which is what they were supposed to be gapped to by NGK. Appalling. I had so much trouble believing it I literally double and triple checked especially the 0.022" one. I used feeler gauges and the wire type gauge to check. I got the tool at advanced autoparts that has both wire and feeler gauges in one. I used to use one of those round keychain type ones but was afraid to break the iridium tip (these are my first iridium plugs) so I got the feeler gauge.


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## XtremeRevolution (Jan 19, 2012)

sedanman said:


> They were all close to 0.025" except that one. So I think it was 0.022", 0.025", 0.025", 0.026"
> 
> Not one of them even hit 0.027" which is what they were supposed to be gapped to by NGK. Appalling. I had so much trouble believing it I literally double and triple checked especially the 0.022" one. I used feeler gauges and the wire type gauge to check. I got the tool at advanced autoparts that has both wire and feeler gauges in one. I used to use one of those round keychain type ones but was afraid to break the iridium tip (these are my first iridium plugs) so I got the feeler gauge.


Yeah, you're definitely not the only one who was baffled to put it mildly. Thanks for reporting back. I've added your results to the spreadsheet.


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## XtremeRevolution (Jan 19, 2012)

Stacy responded to my private message saying she will get in touch with her internal resources and will let me know what the correct spark plug gap and automatic transmission fluid capacity is no later than tomorrow.


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## Calintz (Jul 21, 2011)

Hey guys ever since I gapped my spark plugs to .035 I been hearing a faint knocking noise. I don't know if its due to the increase in gap size on the spark plugs but I was wondering if you guys experience the same issues? I have the 1.8L motor and I hear the ticking which is normal but that faint knocking noise got me a little worried.


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## XtremeRevolution (Jan 19, 2012)

Calintz said:


> Hey guys ever since I gapped my spark plugs to .035 I been hearing a faint knocking noise. I don't know if its due to the increase in gap size on the spark plugs but I was wondering if you guys experience the same issues? I have the 1.8L motor and I hear the ticking which is normal but that faint knocking noise got me a little worried.


Is the noise repetitive with RPMs, and does the frequency of the noise increase as RPMs increase?

Can't say I've noticed anything. Haven't had anyone else report anything either.

What did you torque the spark plugs to?


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## 4piecekit (Mar 17, 2011)

I am awaiting any sort of TSB form GM so I can just have them do it.....but on the other hand, I think I want them gapped to 0.035 so I might do it myself. I am also impatient and like to do anything to my car myself, if it's within reason and my abilities.


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## zippy (May 16, 2012)

XtremeRevolution said:


> Did you run a full tank to notice that 2-3mpg loss?


no, sir. I pulled them when I had a half tank, now I am down to about 1/8th on the same tank. Same hot muggy weather. A/C on like before. same route home and back to work.



XtremeRevolution said:


> I've been scanning with Torque almost daily. Absolutely zero KR unless you're really lugging it at low RPMs.


and you run 89 or better octane, right? a/c on or off? I ask, because a/c causes one big load on a little motor. I am gonna fill up with premium tomorrow and see if my thinking is correct.


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## zippy (May 16, 2012)

also the DA(Density Altitude), has a lot to do with MPG. I noticed a big differance this morning when the cold front came thru. my instant MPG stayed at 38-50 most of my drive and you can feel the "pep in her step". I have ran it a few mornings with no a/c like this morning, and with the larger gap, the MPG is higher than most. The lower the DA, the thicker the air, or higher oxygen content. Like being close to sea level vs in the rockies.


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## XtremeRevolution (Jan 19, 2012)

zippy said:


> no, sir. I pulled them when I had a half tank, now I am down to about 1/8th on the same tank. Same hot muggy weather. A/C on like before. same route home and back to work.
> 
> 
> 
> and you run 89 or better octane, right? a/c on or off? I ask, because a/c causes one big load on a little motor. I am gonna fill up with premium tomorrow and see if my thinking is correct.


There's no way to tell how much of an effect a modification has had with less than half a tank of gas. In fact, it usually requires a good 2-3 tanks of gas to determine what effect there was, if any. The DIC really isn't suitable for this kind of analysis, and environmental factors play a huge role. Even a 5mph headwind will make a difference, as well as humidity level, etc. etc. 

Run 2 more tanks of gas and you'll get a better idea. 

I do run 93 octane from the same gas station at the same pump. This last tank of gas was my lowest in a long time. I went down to 40.3mpg (down from 43.8mpg) as I did a LOT of stop and go traffic with A/C on for more than half the entire tank and temperatures in the low to mid 90s. No issues whatsoever.


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## obermd (Mar 3, 2012)

I liked gman19's idea, so when I picked up my Cruze after having it wallpapered (clear bra for trunk shelf), I asked.

1.4 - 0.85-0.95 mm => 0.0335-0.374 inch - Both were given on the display
1.8 - 0.028 inch - No metric was given

Now I can regap my son's LS.


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## zippy (May 16, 2012)

XtremeRevolution said:


> There's no way to tell how much of an effect a modification has had with less than half a tank of gas. In fact, it usually requires a good 2-3 tanks of gas to determine what effect there was, if any. The DIC really isn't suitable for this kind of analysis, and environmental factors play a huge role. Even a 5mph headwind will make a difference, as well as humidity level, etc. etc.
> 
> Run 2 more tanks of gas and you'll get a better idea.
> 
> I do run 93 octane from the same gas station at the same pump. This last tank of gas was my lowest in a long time. I went down to 40.3mpg (down from 43.8mpg) as I did a LOT of stop and go traffic with A/C on for more than half the entire tank and temperatures in the low to mid 90s. No issues whatsoever.


I would, but it won't be the same. I plan on filling up with 93 tomorrow. I still feel it went down. I go 75 miles round trip, and it would give me a good idea. It may not be down to the exact number, but it is a good tool to use even on short trips. I used it all the time on my LS1 truck, and my G8 while tuning to see if my tuning was close or not. I would reset it, and drive it about 100 miles to get a good avg.


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## Calintz (Jul 21, 2011)

XtremeRevolution said:


> Is the noise repetitive with RPMs, and does the frequency of the noise increase as RPMs increase?
> 
> Can't say I've noticed anything. Haven't had anyone else report anything either.
> 
> What did you torque the spark plugs to?


No the noise doesn't increase when the RPM go up. I think it was a false alarm because this morning I didn't hear anything the knocking noise was gone I think i was was hearing stuff that day lol but in any case I torque my plugs how they were tighten when i first took them out. I'm positive that I didn't over tighten them or under tighten them. I'll keep you posted when I gap them to .040.


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## Jaycruze (Jul 11, 2011)

So the gap is actually spec'd for a larger gap in the smaller 1.4 I'm assuming this is because the 1.4 has a higher compression ratio?

I was going to try .035 in my LS but if it's only supposed to be .028 maybe i shouldn't? I guess there isnt much harm in trying it anyway right?

I wonder if i should try .035 first or .028 first.


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## obermd (Mar 3, 2012)

I'm regapping to the spec. I don't know enough about engines to do otherwise.


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> I'm regapping to the spec. I don't know enough about engines to do otherwise.


For the 1.8, I've recommended .028" as that's what the service manual states, while noting the experiences others have had with that engine at .035". For the 1.4L, my recommendations again were to follow the service manual. Which spec are you referring to?



As a side note, this story is developing into a bit of a storm over at GM per my talks with Stacy. Without divulging too much information until I get a definitive answer, let's just say GM Powertrain is casting doubts on the accuracy of the GM service manual with regard to spark plug gap spec. Whether this is to avoid a major change in assembly line specification (would now need two different spark plug gaps instead of just one), to avoid the cost in printing and mailing out new owner's manuals, to avoid the publicity they would receive and the fallout from half a million owners who will demand that their own spark plug gaps be corrected, or to truthfully correct the specification in all literature is not clear to me. I'm not sure if it ever will be. 

The auto trans fluid capacity spec has not yet been commented on. 

As I have done throughout this thread, I will continue to recommend what the GM service manual recommends, and will keep people posted if that changes.


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## AkotaHsky (Feb 11, 2012)

I gapped mine today to .28. Mine were all below .25, I did not get exact measurements.


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## AkotaHsky (Feb 11, 2012)

BTW -

Mine is a tuned 1.4L and this should be the correct GAP for a TUNED 1.4


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> For the 1.8, I've recommended .028" as that's what the service manual states, while noting the experiences others have had with that engine at .035". For the 1.4L, my recommendations again were to follow the service manual. Which spec are you referring to?


You and I have the same spec and source - the GM service manual. I don't know if your's is from a printed manual, but the one I saw was on my service advisor's computer that he brought up in response to my question.


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> You and I have the same spec and source - the GM service manual. I don't know if your's is from a printed manual, but the one I saw was on my service advisor's computer that he brought up in response to my question.


PM incoming...


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## obermd (Mar 3, 2012)

AkotaHsky said:


> BTW -
> 
> Mine is a tuned 1.4L and this should be the correct GAP for a TUNED 1.4


Assuming you have a Trifecta tune, 0.025. This is according to Vince @Trifecta. He did all the testing on the tune at 0.025.


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## zippy (May 16, 2012)

stick with .025 if he has done all his tuning off .025. changing it will throw off the tune.


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## XtremeRevolution (Jan 19, 2012)

zippy said:


> stick with .025 if he has done all his tuning off .025. changing it will throw off the tune.


Eh, very marginally. Steve @ Insanespeed has had great results on .027. Boats is running wonderfully at .029. Try it out and see what works best. The way Steve put it, a lower gap will make it run like it's on bad gas, but a higher gap will cause blowout. Find a sweet spot, and it's up to you to determine that.


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> Eh, very marginally. Steve @ Insanespeed has had great results on .027. Boats is running wonderfully at .029. Try it out and see what works best. The way Steve put it, a lower gap will make it run like it's on bad gas, but a higher gap will cause blowout. Find a sweet spot, and it's up to you to determine that.


This is true for all engines.


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## Jim Frye (Mar 16, 2011)

I'm sorry if this was posted in the previous 39 pages of this thread, but who makes the plugs for the Cruze? I really am too lazy to read all those posts.


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## coinneach (Apr 10, 2012)

Ngk.


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## Jim Frye (Mar 16, 2011)

Thanks, I just found a page with someone naming them. I'll bet someone in GM changed the specs on the gapping and neglected to tell the manufacturer. Why they are not consistent is a whole 'nuther story.


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## XtremeRevolution (Jan 19, 2012)

Thanks to 70AARCUDA, I now have more fuel to add to this fire. He found the white paper from the EPA for the emissions testing for both the 1.4T and 1.8 motors which also provides a specification for the spark plug gap. Would anyone here be surprised if I told them that this is also different from all of the other gaps we've found so far?

http://iaspub.epa.gov/otaqpub/display_file.jsp?docid=24271&flag=1

The exact number in that paper (page 47) is "0.0236 - 0.0276 inch Gap." 

That's funny...why does that number look familiar? Oh, right, because the service manual is only one number off: .0*3*36-.0*3*76!

Is this the as-tested gap, or is this what the gap is supposed to be? Was there an error in the gap set in the test group, or is there an error in the service manual? Was the spark plug updated at one point, or was it always wrong to begin with? 

How many licks does it take to get to the center of a tootsie pop?

In light of the vast number of conflicting "sources," I find myself unable to make *any *recommendation for what the spark plug gap _should _be, leaving it to each Cruze owner to determine which source of information they want to trust.

The saga continues...


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## Skilz10179 (Mar 22, 2011)

Sounds like the majority of peoples plugs were at those specs from the factory.


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## obermd (Mar 3, 2012)

Skilz10179 said:


> Sounds like the majority of peoples plugs were at those specs from the factory.


... on which the car drives like s**t when compared to 0.035". In addition, I have determined that I *cannot* run 87 octane at 0.025", but that I can at 0.035". So either we should all be running 91 octane or the plugs are the wrong gap.


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## jblackburn (Apr 14, 2012)

^^What he said. I'm sure they didn't intend for the car to run like a boggy piece of junk at the ~.023" or *lower* that my plugs were set at across the board.

It feels to me like it runs like it's supposed to now. I was mad that I bought the car thinking it would run on 87, and it would bog or stall most of the time running on 87. The gap number must have been mixed up in some official publication along the way & that also made its way to the EPA that tested the cars.


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## XtremeRevolution (Jan 19, 2012)

jblackburn said:


> ^^What he said. I'm sure they didn't intend for the car to run like a boggy piece of junk at the ~.023" or *lower* that my plugs were set at across the board.
> 
> It feels to me like it runs like it's supposed to now. I was mad that I bought the car thinking it would run on 87, and it would bog or stall most of the time running on 87. The gap number must have been mixed up in some official publication along the way & that also made its way to the EPA that tested the cars.


This and what obermd is my suspicion of what happened. All of our cars simply run much too well for .024-.028 to be the correct gap. Kinda makes me wonder what the emissions would be on this car if they had tested it with the "newer" gap.


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## Skilz10179 (Mar 22, 2011)

obermd said:


> ... on which the car drives like s**t when compared to 0.035". In addition, I have determined that I *cannot* run 87 octane at 0.025", but that I can at 0.035". So either we should all be running 91 octane or the plugs are the wrong gap.


My car ran fine on the stock gap and 87 octane when it was stock.


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## XtremeRevolution (Jan 19, 2012)

Skilz10179 said:


> My car ran fine on the stock gap and 87 octane when it was stock.


Mine ran, but that's about as much as I can say for it. After going to 93 octane, I could never bring myself to go back down to 87.


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## brian v (Dec 25, 2011)

Something of value to ad to this thread.
All of these issues with ngk iridium plugs are caused from the mills that produce them .
Consider that they are mass produced on a huge scale with little or no quality controls , resulting in defects............
Also we use sae . Pacific rim and europe uses metric measurements............hence milimeters 0.028 installed dwell


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> This and what obermd is my suspicion of what happened. All of our cars simply run much too well for .024-.028 to be the correct gap. Kinda makes me wonder what the emissions would be on this car if they had tested it with the "newer" gap.


The problem with the EPA testing is that it is always done with pure 100% 91 octane gasoline. Our cars run properly on 91 octane at the 0.025" gap. They don't run properly on the 87 octane listed in the owners manual. The Volt's owner's manual states 91 octane and it is running the same base 1.4 engine that all North American non-LS versions of the Cruze run.

If the car is supposed to run on 87 octane, it _*MUST*_ be tested on 87 octane. Basically, the EPA still doesn't get it. Cars need to be tested on (or at least as close to as possible) the same fuel that we purchase. I suspect if a Cruze with 0.025" had been tested on 87 octane GM would have fixed this before the first car hit the dealership lots.


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## obermd (Mar 3, 2012)

brian v said:


> Something of value to ad to this thread.
> All of these issues with ngk iridium plugs are caused from the mills that produce them .
> Consider that they are mass produced on a huge scale with little or no quality controls , resulting in defects............
> Also we use sae . Pacific rim and europe uses metric measurements............hence milimeters 0.028 installed dwell


If you give your supplier the wrong spec, they'll deliver the wrong spec. The variance is NGK's issue, but the peak at 0.025" is GM's issue.


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## XtremeRevolution (Jan 19, 2012)

Might be worth noting that Stacy hasn't responded to my last PM since 06/01/12, exactly one week ago. She even said she'd get back to me on Monday, which she didn't. 

I'll shoot her another PM as a reminder, and if I don't get a definitive answer on some of this (including why EPA's tested gap differs from all GM resources) early next week, I'll start contacting local media. This thread and my case should have made plenty of noise at GM by now for them to realize that I'm not screwing around.


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## XtremeRevolution (Jan 19, 2012)

I guess my last message caught her attention. Stacy claims the correct gap is .028" per a "subject expert" at GM, and recommended that I forward anyone to her if they are having issues. The exact words in a previous email were all bolded, saying the owner's manual is CORRECT and the service manual is WRONG. Either they have nothing better than a trained monkey writing that service manual, or they're trying to get me to go away. I wonder if that "subject expert" is actually from GM Powertrain, or from legal/risk management. 

Interesting...the service manual is still .033-.037. 

Stacy would be able to coordinate with a dealership to have someone bring their car in if they contacted her, but chances are they'll check their shop service manual (which I believe is online and kept up to date), and find .033-.037 to gap the spark plugs to. Will Stacy argue with the dealership and force them to gap to .028 when their service manual shows .033-.037? Doubt it...

Apparently word hasn't gotten around to customer support either. They still read off the owner's manual, and if questioned, they'll recommend that you contact your dealer as the dealer will be the authority on what exact specifications are.

Another interesting note: this "subject expert" Stacy communicated with via email only responded to her question regarding the spark plug gap, not the question she also asked about the auto trans fluid capacity, so last week on Friday she sent another email repeating that question. She says she hasn't received a reply yet. Two emails and nearly 2 weeks go by and GM powertrain has no idea what the auto trans spec should be? 

Sounds more to me like they don't want to admit fault, on both accounts. Admitting fault would probably require them to assume responsibility.

We'll see if Stacy ever gets a reply. Anyone can give an answer for what the spark plug gap should be and there isn't much you can say to fight it, but that auto trans will hold a specific amount of fluid, and they can't just tell me it holds a total of 4.2 quarts if I can drain 5.8 quarts out of it...


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## 70AARCUDA (Nov 14, 2010)

...maybe this guy _within_ *GM-Powertrain *might have be able to find an answer:

*Tom Read
*Technology Communications, Powertrain
Mobile: 248.496.0852 
GM Renaissance Center 
Global HQ | 100 Renaissance Center, 482-A38-D16, C64 | Detroit, Mich. 
48265
GM Powertrain Engineering HQ, 
Bldg. C | 895 Joslyn Ave., 483-710-201, 2L08 | Pontiac, Mich. 48340


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## XtremeRevolution (Jan 19, 2012)

70AARCUDA said:


> ...maybe this guy _within_ *GM-Powertrain *might have be able to find an answer:
> 
> *Tom Read
> *Technology Communications, Powertrain
> ...


I wonder if he would even respond to my email, lol! I'm tempted to send him one...


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## XtremeRevolution (Jan 19, 2012)

I sent a thorough and respectful email to Tom Read, stating that my question regarding the correct spark plug gap was being asked on behalf of this entire community. I will report back if I receive a reply.


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> I guess my last message caught her attention. Stacy claims the correct gap is .028" per a "subject expert" at GM, and recommended that I forward anyone to her if they are having issues. The exact words in a previous email were all bolded, saying the owner's manual is CORRECT and the service manual is WRONG. Either they have nothing better than a trained monkey writing that service manual, or they're trying to get me to go away. I wonder if that "subject expert" is actually from GM Powertrain, or from legal/risk management.
> 
> Interesting...the service manual is still .033-.037.
> 
> ...


I'll stick with the 0.035" that I saw on the Service Manual display. The performance difference is way to noticeable.


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## obermd (Mar 3, 2012)

XtremeRevolution said:


> I sent a thorough and respectful email to Tom Read, stating that my question regarding the correct spark plug gap was being asked on behalf of this entire community. I will report back if I receive a reply.


Thank you.


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## XtremeRevolution (Jan 19, 2012)

obermd said:


> I'll stick with the 0.035" that I saw on the Service Manual display. The performance difference is way to noticeable.


Same here. You and everyone else gapping to .035 have had too many great results to gap back down.

Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


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## rubiconjp (Feb 10, 2012)

Thanks XR and others for your efforts in tracking this down for all of us. I want to regap but also want to know the correct spec. 

Sent from my Galaxy Nexus using AutoGuide.Com Free App


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## XtremeRevolution (Jan 19, 2012)

rubiconjp said:


> Thanks XR and others for your efforts in tracking this down for all of us. I want to regap but also want to know the correct spec.
> 
> Sent from my Galaxy Nexus using AutoGuide.Com Free App


Its more important to make sure they're consistent. I would do it even if you gap them to .028. At least they'll be consistent then and the engine will run smoother because of that alone.

Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


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## MonkeyRench (Feb 10, 2012)

Plant managers give answers when GM call centers or service deparments can't/won't... If you really want to know give him a call. I'd bet everything in my power that he'll get it to you if a end customer calls him. Tell him the scenario and go from there. 
*
Bob Parcell-Plant Manager of Lordstown GM*
2300 Hallock Young Rd SW, Warren, OH 44481
(330) 824-5000


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## David1 (Sep 16, 2011)

Did mine yesterday. All of my plugs were at *.019*! I set them at *.032*. 2011 echo auto with 20k miles. It drives like a different car! It actually moves off the line in city traffic now where before it was almost undrivable in traffic with the air on with ambiant temps at 80 or higher. For some reasson the trans now shifts way better and the lag is gone! Again, it's like a new car.


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## wallbngr (Feb 2, 2012)

David1 said:


> Did mine yesterday. All of my plugs were at *.019*! I set them at *.032*. 2011 echo auto with 20k miles. It drives like a different car! It actually moves off the line in city traffic now where before it was almost undrivable in traffic with the air on with ambiant temps at 80 or higher. For some reasson the trans now shifts way better and the lag is gone! Again, it's like a new car.


Yes I did mine about2 weeks ago .035 and I have tha same results ,Iv' kinda been following this and the Spark Plug Gaps are ALL OVER the Place , Yours are the smallest Iv'e seen here . I'm Surprised it even ran . I would almost bet the color was cool when you lookde at them.
I've been tracking the gas miliage on my Commute and Before Gap I was Getting 1.3 gallons on the downhill side and 1.8 on the uphill side , Now I get 1.1 and 1.6 Respectively ..


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## laugh222 (Apr 17, 2012)

Check the gap. I had an appt. at dealer this AM to run diagnosis to find problem with MPG's. 22-24 hwy. Asked them to check the gap and sure enough the diagnosis said random mis-fire. All 4 gapped wrong. Replaced plugs with proper gap(.028) and the car IS a whole new beast. Runs smoother and MPG's on HWY went from 22 to 37. The sluggishness on take off was always blamed on the tranny, its not the tranny its the gap!!!!!


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## RodM (Apr 24, 2012)

Thanks Xt for following up with this. I think I will be checking mine this weekend. The gas mileage started out at around 35 average and now is only around 32 with ~3000 miles on it. Is it also possible that I should get my first oil change, even though it's supposed to have synthetic oil in it?


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## XtremeRevolution (Jan 19, 2012)

RodM said:


> Thanks Xt for following up with this. I think I will be checking mine this weekend. The gas mileage started out at around 35 average and now is only around 32 with ~3000 miles on it. Is it also possible that I should get my first oil change, even though it's supposed to have synthetic oil in it?


Your car has a synthetic blend oil right now. I wouldn't go past 6,000 miles with that oil with light and highway driving. I'd say 5,000 miles is safe. When you change the oil, put some real synthetic oil in there like Mobil 1 Full Synthetic.


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## den1845 (Mar 14, 2012)

I re-gaped mine last night to.35 and this morning I notice the service engine light is on... What did I do???


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## Macman (May 4, 2011)

den1845 said:


> I re-gaped mine last night to.35 and this morning I notice the service engine light is on... What did I do???


Just a guess, but did you torque them to 18ftlb when replacing them?


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## jblackburn (Apr 14, 2012)

den1845 said:


> I re-gaped mine last night to.35 and this morning I notice the service engine light is on... What did I do???


Pull the rail thingy back off and make sure that all of your springs are straight before pushing it back down.


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## den1845 (Mar 14, 2012)

No I did not torque them...is torquing them real important? I will pull the rail off and check the springs inside the boots when I get home.

Well I think the problem was the springs in the spark plug boots. Found two bent over. Cleared the light... Seems to be fine now


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## jblackburn (Apr 14, 2012)

den1845 said:


> No I did not torque them...is torquing them real important? I will pull the rail off and check the springs inside the boots when I get home.


So long as they're snug enough, no. Don't overtighten them or leave them super loose. I've done my own work on cars for 10 years...the only things that really need a torque wrench are suspension components and head bolts. The rest is just common sense really - "tight enough" will do it for most things.


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## RodM (Apr 24, 2012)

Thanks. That's what I was thinking also. I have 4 free oil changes from the dealer where I bought the car. They will probably use the blended, but maybe they would use full synthetic if I pay the extra cost for the oil. I was just going to wait till when I changed the oil myself to use the full synthetic.


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## XtremeRevolution (Jan 19, 2012)

RodM said:


> Thanks. That's what I was thinking also. I have 4 free oil changes from the dealer where I bought the car. They will probably use the blended, but maybe they would use full synthetic if I pay the extra cost for the oil. I was just going to wait till when I changed the oil myself to use the full synthetic.


Just remember that you can't go off of the oil life monitor to determine when your oil needs to be changed if using the Synthetic Blend from GM.


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## XtremeRevolution (Jan 19, 2012)

MonkeyRench said:


> Plant managers give answers when GM call centers or service deparments can't/won't... If you really want to know give him a call. I'd bet everything in my power that he'll get it to you if a end customer calls him. Tell him the scenario and go from there.
> *
> Bob Parcell-Plant Manager of Lordstown GM*
> 2300 Hallock Young Rd SW, Warren, OH 44481
> (330) 824-5000


You get a busy signal if you try calling that number. That said, I'll check in with Tom Read to see if he was able to get any information.


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## David1 (Sep 16, 2011)

XtremeRevolution said:


> Just remember that you can't go off of the oil life monitor to determine when your oil needs to be changed if using the Synthetic Blend from GM.



The oil life monitor is just fine. My other cars go 20k miles between changes with oil life monitors and I have over 100k on them no problems. The Cruze oil change at around 10k miles is fine. I have been doing extended oil draind for 15 years, on cars so specified with the correct oil, with no problems.


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## Sweber (Jun 11, 2012)

I bought my cruze last Sunday and checked the gaps today. from driver side to passenger side I got; .026, .027, .028, .028. so they were all within the factory spec if the number you reported earlier are correct but I opened them up to .035 anyways and I noticed a slightly better performance.


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## XtremeRevolution (Jan 19, 2012)

David1 said:


> The oil life monitor is just fine. My other cars go 20k miles between changes with oil life monitors and I have over 100k on them no problems. The Cruze oil change at around 10k miles is fine. I have been doing extended oil draind for 15 years, on cars so specified with the correct oil, with no problems.


Did you even wonder why I said that? Oil testing analysis has been done on the factory ACDelco synthetic blend oil and has shown it is unsuitable to be used for the duration of the oil life monitor, which for many of us is 10k miles. In fact, many dealerships have noted that the oil is only suitable for a 6k mile interval. There are several threads on this topic that I suggest you find and read. The only way the oil life monitor can be trusted is when using a quality full synthetic oil. 

Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


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## blk88verde (Apr 30, 2011)

I changed the Dexos 1 at 1k miles and switched to Mobil1 and new AC Delco filter. I never reset my oil life monitor. Now at about 7,800 miles, the OLM is lighting at 5% oil life. I plan on changing the oil and filter this weekend-eventhough there are probably a few thousand more miles of life in it. With the Cruze, oil life depends on how you drive, I do a lot of very short trips. Engine may not fully warm up especially in the winter. I had a 2002 Mercedes C230K that used a mileage only system. At every 10k an "A Maintenance" light would pop up - meaning oil and filter change. This was probably fine since the factory fill was Mobil 1.


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## oshia86 (May 29, 2011)

My car has been in the shop for the last month to be repaired from a recent hail storm. Go figure once that happens something like this would come up and it will be a while before I am able to check the car. Now, the .035 gap is recommended for a stock car, regardless of octane?


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## XtremeRevolution (Jan 19, 2012)

oshia86 said:


> My car has been in the shop for the last month to be repaired from a recent hail storm. Go figure once that happens something like this would come up and it will be a while before I am able to check the car. Now, the .035 gap is recommended for a stock car, regardless of octane?


.035" is what I and many others will recommend as we've found the car runs very, very nicely on that gap with notable improvements in fuel economy. This is indeed regardless of octane. In fact, some have found that the car requires higher octane fuel to even run decently with the stock gap, while raising the gap to .035" allows them to run 87 octane smoothly again.


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## David1 (Sep 16, 2011)

XtremeRevolution said:


> Did you even wonder why I said that? Oil testing analysis has been done on the factory ACDelco synthetic blend oil and has shown it is unsuitable to be used for the duration of the oil life monitor, which for many of us is 10k miles. In fact, many dealerships have noted that the oil is only suitable for a 6k mile interval. There are several threads on this topic that I suggest you find and read. The only way the oil life monitor can be trusted is when using a quality full synthetic oil.
> 
> Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


It is just fine. Trust me. No motors are blowing up from lack of oil service with this engine family.


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## XtremeRevolution (Jan 19, 2012)

David1 said:


> It is just fine. Trust me. No motors are blowing up from lack of oil service with this engine family.


Nobody said they'd blow up, but when the engine oil has exhausted all detergents and its ability to provide adequate lubrication and protection against contaminants past 6000-7,500 miles, and the oil life monitor recommends 10,000 miles, you can be sure that I won't be using or recommending it for 10,000 miles. Once the detergents are gone and the contaminant levels start to rise, you start leaving deposits around the motor. It's particularly important as the turbo is more sensitive to proper lubrication. If you don't believe me, do a search around this site. Oil testing analysis has been done on the factory ACDelco synthetic blend oil, the results have been posted before, and they're not pretty. 

You may have your own opinions, but the facts are against them and as such, I cannot recommend what you claim is perfectly fine for the motor. No, the engines won't blow up. It takes a lot to "blow up" an engine, but that doesn't mean gunk won't be deposited around the engine over time, and that doesn't mean you won't have problems down the line. By 100,000 miles? Probably not, but some of us will keep our cars longer than that. 100k miles is really all GM cares about as that's the extent of their powertrain warranty. I kept my last car till 240k miles, and I intend to do the same with the Cruze.

It's your word against the professional oil testing analysis at Blackstone Labs saying the oil is not suitable for further service. Not to be rude, but while you are certainly free to do what you wish, you're not going to be convincing me to go 10,000 miles on GM's oil.

For more info, visit bobistheoilguy.com. They'll make your head spin with how much they know about automotive oils. Much of what I'm saying, I've learned from the hours I've spent reading threads on that site.


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## Chevy Customer Care (Oct 29, 2011)

laugh222 said:


> Check the gap. I had an appt. at dealer this AM to run diagnosis to find problem with MPG's. 22-24 hwy. Asked them to check the gap and sure enough the diagnosis said random mis-fire. All 4 gapped wrong. Replaced plugs with proper gap(.028) and the car IS a whole new beast. Runs smoother and MPG's on HWY went from 22 to 37. The sluggishness on take off was always blamed on the tranny, its not the tranny its the gap!!!!!




laugh222,
I am happy to hear that your dealer was able to get this issue resolved for you. I am also happy to hear that your vehicle is performing better! If you have any other questions, comments or concerns please feel free to contact me.
Thank you,
Stacy Chevrolet Customer Service


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## David1 (Sep 16, 2011)

XtremeRevolution said:


> Nobody said they'd blow up, but when the engine oil has exhausted all detergents and its ability to provide adequate lubrication and protection against contaminants past 6000-7,500 miles, and the oil life monitor recommends 10,000 miles, you can be sure that I won't be using or recommending it for 10,000 miles. Once the detergents are gone and the contaminant levels start to rise, you start leaving deposits around the motor. It's particularly important as the turbo is more sensitive to proper lubrication. If you don't believe me, do a search around this site. Oil testing analysis has been done on the factory ACDelco synthetic blend oil, the results have been posted before, and they're not pretty.
> 
> You may have your own opinions, but the facts are against them and as such, I cannot recommend what you claim is perfectly fine for the motor. No, the engines won't blow up. It takes a lot to "blow up" an engine, but that doesn't mean gunk won't be deposited around the engine over time, and that doesn't mean you won't have problems down the line. By 100,000 miles? Probably not, but some of us will keep our cars longer than that. 100k miles is really all GM cares about as that's the extent of their powertrain warranty. I kept my last car till 240k miles, and I intend to do the same with the Cruze.
> 
> ...


Yup, and the hours you spent on that site is lost time. It's not a bad read though. I have used blackstone in the past and have better use for my money. I have taken plenty of extended oil drain motors apart even on dino oil and they have been fine. Even on my other cars that are 4 to 5 times the value of a Cruze go 18k to 22k between changes. The less people know about oil condition the least fear there will be. The manufacturers have oil life/reliability down to a science and it works. Then, at about 150k miles a Cruze becomes a consumable (worth almost nothing) that is not worth doing any major repair to. In the end it will not be the oil that ends it's life and sends it off to the bone yard.


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## XtremeRevolution (Jan 19, 2012)

David1 said:


> Yup, and the hours you spent on that site is lost time. It's not a bad read though. I have used blackstone in the past and have better use for my money. I have taken plenty of extended oil drain motors apart even on dino oil and they have been fine. Even on my other cars that are 4 to 5 times the value of a Cruze go 18k to 22k between changes. The less people know about oil condition the least fear there will be. The manufacturers have oil life/reliability down to a science and it works. Then, at about 150k miles a Cruze becomes a consumable (worth almost nothing) that is not worth doing any major repair to. In the end it will not be the oil that ends it's life and sends it off to the bone yard.


I guess this is where we disagree. To me, a 150,000 mile car does not become consumable. If my wife's transmission on her 2000 Regal GSE goes out (bought it with 151k and now has 162k), we're going to replace the transmission or have it rebuilt and move on. 

The Cruze (particularly my Cruze Eco) is in an even better position, having the manual transmission. What's the cost of a clutch these days? Talking to Travis, he noted that this is by far the easiest clutch he's ever had to replace on a car. He was unlucky enough to have a defective one from the factory and didn't want to chance getting another defective one. I intend to keep this vehicle at least 10 years, which at the rate I'm driving will probably have me at just over 180k miles, and by that point, I want to be able to sell it, not scrap it for a few tanks' worth of gas. 

Any repairs needed on this vehicle at under 150k miles will be relatively minor, inexpensive, and will likely not be powertrain related. Maybe a small gasket here and there. I'd hardly call this car disposable by that point. Perhaps "broken in." I guess we don't all have the luxury of having cars that are worth 4 to 5 times as much as the Cruze, so what oil we use and what interval we change it will probably matter a bit more. I will be genuinely disappointed if I don't personally put 200k miles on this car. 

Blackstone says GM oil isn't suitable for 10k mile intervals? No problem. I do my own oil anyway, and I know the Mobil 1 Full Synthetic oil I use is in fact suitable for the 10k mile interval. If you caught that, my argument is not against the oil change interval specifically (no need to bring up how scientifically accurate it is), but against the interval with the ACDelco synthetic blend oil that the dealers will put in the car during an oil change.


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## oshia86 (May 29, 2011)

David1 said:


> Yup, and the hours you spent on that site is lost time. It's not a bad read though. I have used blackstone in the past and have better use for my money. I have taken plenty of extended oil drain motors apart even on dino oil and they have been fine. Even on my other cars that are 4 to 5 times the value of a Cruze go 18k to 22k between changes. The less people know about oil condition the least fear there will be. The manufacturers have oil life/reliability down to a science and it works. Then, at about 150k miles a Cruze becomes a consumable (worth almost nothing) that is not worth doing any major repair to. In the end it will not be the oil that ends it's life and sends it off to the bone yard.


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## 70AARCUDA (Nov 14, 2010)

...sounds like an obvious "case" of _differing_ *mindsets*:

• the *CONSUMABLES* who view a _*used car *_as "throw-away" appliances.

...versus:

• the *DURABLES* who view a _*used car *_as a "lasting" investment worthy of _continued_ maintenance.


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## obermd (Mar 3, 2012)

70AARCUDA said:


> ...sounds like an obvious "case" of _differing_ *mindsets*:
> 
> • the *CONSUMABLES* who view a _*used car *_as "throw-away" appliances.
> 
> ...


I consider a car a consumable, but I expect it to last at least 150,000 miles. My decision to replace is based almost entirely on how much is it costing to keep it repaired (not routine maintainence) vs the cost of a new car payment.


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## sirjr (Mar 27, 2012)

I re-gaped my plugs this morning. My plugs were gaped at .025 - .026. I used a torque wrench to remove the plugs as I wanted to see what the torque was from the factory. Three of the plugs were 17 ft-lbs. One was at 30 ft-lbs! I re-installed all at 17 ft-lbs. Thanks to all that posted about the springs as one of my springs was at an angle, even though I pulled the coil assembly straight up. I would have never thought about looking inside. I'll let everyone know what my MPG changes are.


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## David1 (Sep 16, 2011)

70AARCUDA said:


> ...sounds like an obvious "case" of _differing_ *mindsets*:
> 
> • the *CONSUMABLES* who view a _*used car *_as "throw-away" appliances.
> 
> ...


Yup, just difference of opinions, personal experience and constructive arguing. My cruze is leased so it doesn't get one extra penny spent on it especially oil. It's due for its second oil change, it's been 13k miles and then GM can have it back with all the service consumables used up in a few months.


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## ManthaBurner (Jul 4, 2011)

I finally took the time to pop the hood on my 2011 eco, not a gear head by anyones standards. I took everyones advice wit the tools and such and what do i find? 2 plugs are at .026 and the other 2 are at .027! Re-gapped those little bastards up to .035 and it did totally make a difference. I called up my dealer before this and they said it would cost me to have them do it unless the gap was off, then being covered by the warrenty so obviously I did it on my own.

I just got back from a little drive and instantly felt the difference. I didnt feel anything off at all either but should probably data log so Vince can take a peak at everything incase anything like fuel trims are thrown off a little with the gaping and my K&N SRI.


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## RodM (Apr 24, 2012)

I took my Cruze to the dealer to have the Auto Climate control fixed by a software update and asked if they could check the spark plug gap. Had to tell them it was sluggish during initial movement from start. I am not at all happy with the outcome of the service that was performed. I had two concerns. One was the fan speed and cooling while utilizing the Auto Climate Control and the other was a concern with the spark plug gap. After 3 hours I was told my car was ready and that there was nothing wrong with the Climate Control because it cooled to 69. That wasn’t my concern because I knew it would cool. My concern was when the inside was already at 69 and I set the temperature to 75 the fan still blows cold air at a high speed. It would only slow if I set the control to a higher temp like 82. I will not use the Auto Climate Control if it continues to act like this. I was told there was no update available for my VIN#. As far as the spark plug Gap goes, I was first told that the Gaps were set properly. When I assisted that we ask the mechanic if he had actually checked the gap because I knew they were not set properly to begin with, I was told there was a misunderstanding and that he actually did not check them because he couldn’t find any reason to. I ended up re-gapping them myself. They were all set to .025. I set them to .035 and did notice a small difference in exceleration however I think I have lost about 2-3 MPGs. So what is the gap supposed to be? The Service manager pulled up his information and it said .033 - .037

To make things more confusing, when I used the car the following day, the fan speed seemed to work. As a matter of fact it may be too slow now, but I would rather it be that way then the other. If there was no update, why is it now somewhat working? I don’t like being lied to even if it is a misunderstanding. There’s obviously a lack of communication somewhere. I have not yet received a Customer Maintenance manual that was missing when took delivery of the car.


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## XtremeRevolution (Jan 19, 2012)

How exactly did you measure a 2mpg loss?

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## 98sonoma (Nov 30, 2010)

Xtreme, have you heard anything more from GM about this?


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## XtremeRevolution (Jan 19, 2012)

98sonoma said:


> Xtreme, have you heard anything more from GM about this?


Yes. I got an official email from Tom, approved by product engineering, service engineering, and manufacturing engineering at GM. I'll post it in a new thread once I get back from vacation.

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## 98sonoma (Nov 30, 2010)

XtremeRevolution said:


> Yes. I got an official email from Tom, approved by product engineering, service engineering, and manufacturing engineering at GM. I'll post it in a new thread once I get back from vacation.
> 
> Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


Great, thank you!

Enjoy your vacation!


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## Macman (May 4, 2011)

Just filled up, 2nd tank after regapping, 31.7 mpg according to fuelly. last 2 tanks since regap is around 450 miles, improved.


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## icwe2 (Jul 1, 2012)

Hey everyone, Just bought a 2012 Eco AT for the wife back in may has 1400 miles on it as of right now. Just went down to autozone and picked up the essentials to see what my gap is on my plugs ill re-post mine here after a while.

just got done first plug i pulled I noticed right off the bat it was already dirty for only having 1400 miles so I knew right away it was not burning clean. From left to right 2012 Eco AT manf. in apr 2012 .*026, .028, .024, .025 *I adjusted them all to .035 and noticed a difference right away in the idle. its def a lot quieter and runs smoother. When I went for a drive I noticed the acceleration seemed better and all together seemed as if the car ran much much smoother thanks everyone for the info to get this taken care of.


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## rallycar2001 (Jul 1, 2012)

XtremeRevolution said:


> Got this from a buddy of mine on w-body.com. Click to enlarge.
> 
> ECO:
> 
> ...


EDIT EDIT EDIT! 
do not run more than .30 on 1.8! i just had some kid come to my dealer with a drivability problem "stumble and hesitation under initial wot"
the coil pack on 1.8 is not as strong as the 1.4! duh the 1.4 is turbo, needs more spark. service information, thru general morors, on my computer, in my stall, states : .28-.30 and 1.4 is .34-.36
alldata is not the same as si. si is compiled by real engineers who work on specific vehicle information.


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## jdubb11 (Mar 14, 2012)

i remember reading at one point that when checking the plugs to check the "springs" because some could bend when checking the plugs. i had my dealer regapp (no fee) and i pulled the plugs to verify that they gapped them to .36, which they did. however i didnt notice anything except the spark plug boots??? '12 1.4t


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## obermd (Mar 3, 2012)

jdubb11 said:


> i remember reading at one point that when checking the plugs to check the "springs" because some could bend when checking the plugs. i had my dealer regapp (no fee) and i pulled the plugs to verify that they gapped them to .36, which they did. however i didnt notice anything except the spark plug boots??? '12 1.4t


The springs are in the rubber boots attached to the coil cover that you have to remove to get to the spark plugs.


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## jdubb11 (Mar 14, 2012)

obermd said:


> The springs are in the rubber boots attached to the coil cover that you have to remove to get to the spark plugs.


ty i didnt look in the boots but car is running good so they must be in there right


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## Atomic (Nov 5, 2011)

Copying the below quote from another spark plug gap thread, since there is related conversation in here.
----------

Just wanted to provide an update.

1st trip - 452 miles on 12.5 gallons = 36.1mpg
Weather conditions were 100 degrees with around 40% humidity and a 5-7mph headwind.
AC was ON the entire trip, cruise control at 70mph.

Spark plug gaps were found to be .024, .024, .027, .026

Regapped plugs to .033

~~~~~~

2nd trip - 452 miles on 13.0 gallons = 34.7mpg
Weather conditions were average temp around 80, humidity about 60%, some rain, winds were a strong headwind for first half of trip, then variable the second half.
AC was ON for half the trip, OFF for the second half, with cruise set at 70mph.

This is not scientific nor indisputable evidence one way or the other, but given the weather variables, *I'd call the spark plug gaps having a noticeable effect on MPG unlikely at best, whether it be positive or negative. I use only 93 octane in the car (10% ethanol) as well.*


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## XtremeRevolution (Jan 19, 2012)

Atomic said:


> Copying the below quote from another spark plug gap thread, since there is related conversation in here.
> ----------
> 
> Just wanted to provide an update.
> ...


You can't use the DIC to accurately measure fuel economy. The only valid metric will be to measure the total fuel economy over several tanks of gas. The variations between individual trips are far too great and the DIC has been proven inaccurate.


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## Atomic (Nov 5, 2011)

My numbers were calculated at the pump, not using the DIC. I also know they are not scientific or indisputable evidence, hence why I said that - just providing more information to be referred to... my results show that there is no meaningful difference to be had using just this 900 mile round trip. I simply posted the results so that there are actual facts to be referred to.


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## mknight (Mar 5, 2012)

XtremeRevolution said:


> Yes. I got an official email from Tom, approved by product engineering, service engineering, and manufacturing engineering at GM. I'll post it in a new thread once I get back from vacation.
> 
> Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


I've been searching for the new thread with the email from GM. Have you had time to post it yet? or maybe I am just blind lol!


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## XtremeRevolution (Jan 19, 2012)

mknight said:


> I've been searching for the new thread with the email from GM. Have you had time to post it yet? or maybe I am just blind lol!


I forgot to post a new thread, lol. I simply posted it in the other "what is your spark plug gap?" thread. Should be one of the most recent posts there.


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## obermd (Mar 3, 2012)

Strong headwinds impact all high MPG cars, not just the Cruze. I noticed your second trip you said you had a strong headwind.


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## metgolf18 (May 10, 2012)

*also incorrect gap*

while I didn't check the gaps prior to regapping. They were diffently wrong. I know they weer all less thsn .025 prior to regap and I have since regapped to .033. It's my wife car andI asked her if she notice a difference and she said yes. There was no hesitation like before. Just to add, my car is a 2011 equinox and I decided to check the plug gaps and found them all to be .025 where they are supposed to be .035, so i regapped thenm to .037. Haven't driven it yest, but will find out how it responds tomorrow.


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## XtremeRevolution (Jan 19, 2012)

Just wanted to report back. I started at .035, tried .040 for 1000 miles, then .038. I've been at .038 for about 3500 miles. Once I installed the Injen intake, I started getting occasional spark blowout around 2000-2500 rpm. I backed down today to .033. This was all done with feeler gauges. No more spark blowout. 

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## Vetterin (Mar 27, 2011)

Re-gaped all mine back down to .028 yesterday.


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## sedanman (Dec 10, 2010)

How do you know if you have spark blowout? Hesitation? I still have mine gapped at 0.034". No more hesitation like I was getting when the gaps were all over the place.


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## jblackburn (Apr 14, 2012)

Spark blowout usually happens at higher RPMs and you'll feel a definitely miss or hiccups in the power delivery.


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## XtremeRevolution (Jan 19, 2012)

sedanman said:


> How do you know if you have spark blowout? Hesitation? I still have mine gapped at 0.034". No more hesitation like I was getting when the gaps were all over the place.


You'll feel something like a misfire. The engine will "hickup" slightly like you just lost power momentarily. It's a very short event, but you'll be able to tell if it's accelerating smoothly. I never had an issue at .035".


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## jblackburn (Apr 14, 2012)

> I never had an issue at .035".


Just curious, what do you have yours set at now? Did you take them back to the .028"? How's it drive if you did?


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## sedanman (Dec 10, 2010)

XtremeRevolution said:


> You'll feel something like a misfire. The engine will "hickup" slightly like you just lost power momentarily. It's a very short event, but you'll be able to tell if it's accelerating smoothly. I never had an issue at .035".


Ok thanks.


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## XtremeRevolution (Jan 19, 2012)

jblackburn said:


> Just curious, what do you have yours set at now? Did you take them back to the .028"? How's it drive if you did?


I now have them set to .033". To me, there's no appreciable difference between .033" and .035".


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## Mustang Jim (Jul 28, 2012)

I just found this forum a week ago and I'm glad I did.

I checked my plugs this morning and I found that they were all gapped at 0.025" (+/- 0.002"). I was not experiencing any appreciable issues prior to regapping to 0.035" today. However, I have found less of a "lag" on initial acceleration after regapping the plugs. I'll keep an eye on the gas mileage and let everyone know where it goes.

Good stuff!


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## sheleb1 (Sep 16, 2011)

I've driven approx. 2,000km with gap at .035" and have experienced no difference in fuel economy.
After the re-gap I did feel that the car seemed more peppy though; especially in the lower gears.
On a couple occations recently I've noticed what might be "spark blowout". With passengers in the car & A/C on, going up hill on the hwy (just maintaining speed) I've felt a few split second hesitations (as if I took my foot off the petal), and also what seemed to be a second long pinging sound yesterday.
I'm thinking of bringing gap down to about .032" now. Using 87 octane.
Any thoughts?


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## XtremeRevolution (Jan 19, 2012)

sheleb1 said:


> I've driven approx. 2,000km with gap at .035" and have experienced no difference in fuel economy.
> After the re-gap I did feel that the car seemed more peppy though; especially in the lower gears.
> On a couple occations recently I've noticed what might be "spark blowout". With passengers in the car & A/C on, going up hill on the hwy (just maintaining speed) I've felt a few split second hesitations (as if I took my foot off the petal), and also what seemed to be a second long pinging sound yesterday.
> I'm thinking of bringing gap down to about .032" now. Using 87 octane.
> Any thoughts?


Sounds a lot more like you're getting some knock. Try it again with a higher octane fuel. The 1.4 Turbo really benefits greatly from higher octane fuel.


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## sheleb1 (Sep 16, 2011)

Okay, will try.
Thanks Xtreme.


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## Cips (May 21, 2012)

I checked mine (.028) and regapped to .035 and running 89 octane. I don't feel a difference at all.


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## XtremeRevolution (Jan 19, 2012)

Cips said:


> I checked mine (.028) and regapped to .035 and running 89 octane. I don't feel a difference at all.


Did you remember to pull the battery cable after adjusting the gap?

Also, what transmission do you have?


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## Cips (May 21, 2012)

XtremeRevolution said:


> Did you remember to pull the battery cable after adjusting the gap?
> 
> Also, what transmission do you have?


No I didn't pull the cable. I have an A6.


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## XtremeRevolution (Jan 19, 2012)

Cips said:


> No I didn't pull the cable. I have an A6.


I would recommend doing that. Having the automatic transmission generally means you won't feel the differences as much as you won't be spending as much time in lower RPMs.


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## Cips (May 21, 2012)

I'll do that tomorrow. Thank you for the suggestion. I must have missed it earlier.


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## hawkeye (Mar 31, 2012)

I missed the pulling the cable part, too. What is the purpose? Maybe that's why I haven't seen any mpg improvement with my ECO automatic?


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## smorey78 (Apr 8, 2012)

i am tuned and running plugs at .029 and maybe every 5 pulls or so in sport mode i will notice a spark blow out (kinda feels just like a missfire) at first i thought i was lifting my foot a lil and the blow off was what i was feeling. other time i can go wot in sport mode and feel nothing and than the next light i will go maybe 80 or 90% and not wot and get spark blow out. so i think i am going to pull them and set them to .027 and hope that stops it for good.


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## XtremeRevolution (Jan 19, 2012)

hawkeye said:


> I missed the pulling the cable part, too. What is the purpose? Maybe that's why I haven't seen any mpg improvement with my ECO automatic?


You pull the cable so you can reset the ECM's fuel trims. The more complete burn will use less fuel to get a given amount of power at low RPMs, and the PCM needs to re-learn the difference.

As fo your mpg difference, it is based on many factors. It has been proven to improve fuel economy, and it certainly has on mine, but it does appear to make most of the difference at low RPMs. If you want to know how much of a difference, you'd have to alternate a few tanks between the larger and smaller gap sizes.

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## 6speed (Dec 7, 2011)

XtremeRevolution said:


> You pull the cable so you can reset the ECM's fuel trims. The more complete burn will use less fuel to get a given amount of power at low RPMs, and the PCM needs to re-learn the difference.
> 
> As fo your mpg difference, it is based on many factors. It has been proven to improve fuel economy, and it certainly has on mine, but it does appear to make most of the difference at low RPMs. If you want to know how much of a difference, you'd have to alternate a few tanks between the larger and smaller gap sizes.
> 
> Sent from my Bulletproof_Doubleshot using AutoGuide.Com Free App


*XtremeRevolution* 

The spark plug gap change has actually driven your MPG down. Your FUELLY shows you have lost 6-7 MPG since spring & the old plug gap. Increasing your city driving by 20% & running some A/C will not change it by that much. You have another cause affecting your ECO. Try a fishbone chart.

How long should the battery cable disconnect be for? I did mine for 3 minutes, is that enough time? Interesting thing how cable disconnect affected my DIC with the engine shut off. Before disconnecting cable, for average MPG, it displayed 50.0. After reconnecting cable, but before starting engine, it displayed 50.1 MPG. 
My plugs from the engine plant were gapped: .025 .025 .025 026 in.
Now they are .035 in.
So far, engine is a little smoother upon acceleration.
Follow my future FUELLY posts to see how it affects my MPG.


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## XtremeRevolution (Jan 19, 2012)

6speed said:


> *XtremeRevolution*
> 
> The spark plug gap change has actually driven your MPG down. Your FUELLY shows you have lost 6-7 MPG since spring & the old plug gap. Increasing your city driving by 20% & running some A/C will not change it by that much. You have another cause affecting your ECO. Try a fishbone chart.
> 
> ...


6speed, you really need to ask questions before making assumptions. The first question you should ask is when I changed my spark plug gap. The second question you should ask is "Is xtremerevolution really dumb enough to not notice something like that?" Trust me, I've been keeping very close track of my calculated FE. 

Look at my fuelly again. I increase my spark plug gap mid-way through fill-up #15, which was at 42.2mpg. I left notes in all of my fill-ups so you could clearly see that fact. The two consecutive fill-ups with the increased spark plug gap read 43.8mpg, and the one after that read 40.3mpg, but also with a note stating that the driving was done with 75% A/C use. 

Following that, my fuel economy began to drop. However, if you read the notes, you'll see that I used A/C nearly 100% of the time. 

6/26/2012 was the first fill-up that my fuel economy dropped below 40mpg since 3/15/2012. It was also coincidentally the day I went on vacation and my posts here became more scarce for 2 weeks following, and was the start of the ridiculous heatwave the country got, which would last another 1.5 weeks. That day, I picked up my brother, sister, and sister's husband from the airport and we drove around for about 150 miles that night. Again, 100% A/C use. 

Following my fill-up on 6/26/2012, the 4 fill-ups would include 100% A/C use as well as an unusually high city driving percentage as I packed my car with 5 people including me (and my sound system in the trunk) and drove them around town. The only exception was the fill-up on 7/2/12, which was a day when my sister and brother in law took my car to visit their aunt in central Illinois. Even with 100% A/C use, that tank still averaged 42mpg. However, 100% A/C use in 90-100% city driving really kills fuel economy. 

Every fill-up after that was taken with 100% A/C use, and at least 2 hours during each tank of gas included my car idling with A/C on while I tuned and tweaked the sound system (which I'm still not done with). They also included teaching my little brother (who decided to stay longer) how to drive a manual. 

This current tank of gas is the first tank of gas I've been able to drive with minimal use of A/C (under 50%) as the temperatures in the morning and evening have been at or under 85 degrees F. 

My DIC is showing 44.2mpg for my current tank of gas.


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## Jaycruze (Jul 11, 2011)

Stupid question, where did you guys get the bit for the engine cover?


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## obermd (Mar 3, 2012)

Jaycruze said:


> Stupid question, where did you guys get the bit for the engine cover?


You can purchase the T30 torx bit just about anyplace you can purchase screwdrivers, including most auto parts stores. Basically it's a star bit. I used a T28 for my ECO MT. T28 worked but I wish I had purchased the T30 instead. Also, if you've lost the link to how to do this here it is: http://www.cruzetalk.com/forum/57-how-forum/6722-diy-re-gap-factory-spark-plugs.html


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## Jaycruze (Jul 11, 2011)

woops i see now, i was trying to remove the wrong part lol... im talking about those funky socket bolts that are on the area below the small engine covers.


its got those security type sockets.

i guess you can only get those at the dealer... but i dont want to remove that part anyway...


QUOTE=obermd;126399]You can purchase the T30 torx bit just about anyplace you can purchase screwdrivers, including most auto parts stores. Basically it's a star bit. I used a T28 for my ECO MT. T28 worked but I wish I had purchased the T30 instead. Also, if you've lost the link to how to do this here it is: http://www.cruzetalk.com/forum/57-how-forum/6722-diy-re-gap-factory-spark-plugs.html[/QUOTE]


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## USAFeco (Jul 20, 2012)

Just checked and corrected (.035) the gaps in my ECO. ( L ---> R .025 / .026 / .025 / .025). Also did the resonator box mod while the hood was up. Should be ordering a drop in K&N soon and we'll see how much it'll improve all around. 

Built date is Feb '12 with 3052 miles as of today.


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## Aftica (Oct 22, 2012)

Thanks for the INFO guys,

Went today to the service manager where I purchased my car and he had not heard of the problem with the spark plug gap. I informed him and he said there were no bulletins about the issue so he couldn't check them. 
I said OK. thanks for nothing.

Took my Cruze to a buddy of mine who is also a top notch mechanic. He checked out the specs with his software and low and behold it is specified at .033 to .037. 
We let the engine cool for a while and he pulled the plugs... Ready for this...

cylinder
#1 = .025
#2 = .022
#3 = .025
#4 = .025

They were all under spec..

I called the service manager back and told him what we found. He replied that they are supposed to be .028 which is close to what we found. I said thanks for nothing but they are now .035 and I am already not happy with your service department. I have already had a call from my friend I purchased the car from apologizing about the incident . I told him that it was a simple request that would take 15 minutes to check and it should have been checked with my questioning it. I am going to meet with him Thursday face to face. I'll let you know what I find out!


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## XtremeRevolution (Jan 19, 2012)

Aftica said:


> Thanks for the INFO guys,
> 
> Went today to the service manager where I purchased my car and he had not heard of the problem with the spark plug gap. I informed him and he said there were no bulletins about the issue so he couldn't check them.
> I said OK. thanks for nothing.
> ...


There was a big debacle over how this whole situation was handled. The spec in the GM Service manual used to also say .0335-.0375, but then they realized they were off one digit after I brought it to their attention and they adjusted it to .0235-.0275. However, the service manuals that other shops used have not yet been updated, and as far as I know, it's still .0335-.0375 out in Australia. 

I've stopped making recommendations as a result. I've tried a large variety of gaps. Currently at .030. .035 felt smoother than .030, but .030 feels like it has a tad bit more bottom end power, but I don't know if it's actual power, or if it's just the additional roughness that makes it feel like there's more power.


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## Vetterin (Mar 27, 2011)

The more I read.......the more confused I get. Do we have a definite gap spec we can go by as I have had my plugs gaped to (in the following order) .025, .032, .030, .035 and currently .028 and really can't say for sure that one gap is better than the other.


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## obermd (Mar 3, 2012)

The current GM Spec for the 1.4T Cruze is 0.025" to 0.0275". The original 1.4T Cruze spec was 0.033-0.037". The 1.8 has always been 0.028". If you have a Trifecta or other tune that increases HP, do not go above 0.028".


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## Vetterin (Mar 27, 2011)

I remember reading that before but does that mean that 0.025" to 0.0275" will yield the optimum results in performance and gas mileage? (THAT'S where I'm confused) My butt-o-meter kinda likes the 0.032" gap overall. I'm also talking strictly un-tuned.


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## obermd (Mar 3, 2012)

Vetterin said:


> I remember reading that before but does that mean that 0.025" to 0.0275" will yield the optimum results in performance and gas mileage? (THAT'S where I'm confused) My butt-o-meter kinda likes the 0.032" gap overall. I'm also talking strictly un-tuned.


Probably not. My butt-o and foot-meters much prefer the 0.035" that I set my ECO MT to. I suspect the smaller gap is to prevent "premature" wear on the coil springs in the plug boots.


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## YKNWT (Oct 6, 2012)

Checked mine today prior to installing the budget tune and they were all between .026 - .027. Bumped them to .029.

2012 Cruze Eco
M/T


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## gt_cristian (Apr 7, 2012)

Vetterin said:


> does that mean that 0.025" to 0.0275" will yield the optimum results in performance and gas mileage?


I am wondering about this too. If we were to increase the gap from .022 - 0.25 to .028 or .032, which one would help MPG?
It would makes sense that .032 will make the engine more responsive and therefore feel more powerfull, but how about MPG?


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## cerbomark (Dec 13, 2010)

Pulled my plugs just to see what the gap was.. It was .024-25 on them all. I ll called my dealer and he said .028 so I re gapped them at 028. I doubt there will be any difference. My car runs fine and I just did a 3000 mile trip and got 34-35MPGs on a highway trip at about 70-79 MPH. I am happy with that as the car had a few hundred pounds of cargo also. I can not find any info that tells me .035. What did I miss?


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## obermd (Mar 3, 2012)

cerbomark said:


> Pulled my plugs just to see what the gap was.. It was .024-25 on them all. I ll called my dealer and he said .028 so I re gapped them at 028. I doubt there will be any difference. My car runs fine and I just did a 3000 mile trip and got 34-35MPGs on a highway trip at about 70-79 MPH. I am happy with that as the car had a few hundred pounds of cargo also. I can not find any info that tells me .035. What did I miss?


First - the fact that all your gaps were consistent is very important. The ECU assumes the gaps are consistent. You might see a slight improvement going from 0.024/0.025 to 0.028. The 0.035 is from the original Chevy on-line service manual for the Cruze. GM engineering has since come out and stated 0.025 - 0.0275" is the correct gap for this car. Many of us who had already regapped to 0.035 have chosen to leave our plugs there.


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## 70AARCUDA (Nov 14, 2010)

The generic "_*Rule-of-Thumb*_" for 'tweeking' spark plug gaps (from OEM number) is:

• *SMALLER* gap for *HP*.
• *WIDER *gap for *MPG*.

Assuming constant energy (Watt-seconds or Joules) from the ignition coil, a *smaller* gap will result in a slightly *longer* duration arc and a *wider* gap will result in a slightly *shorter* duration arc. It is easier for the arc to jump a smaller gap and makes it easier to "initiate" ignition of *rich-*A/F mixtures (rich = HP). A longer arc duration, however, increases both the *area* and *duration* of the arc between the electrodes, greatly increasing the "probability" of ignition of *lean*-A/F mixtures (lean = MPG) promoting more complete combustion.


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## XtremeRevolution (Jan 19, 2012)

70AARCUDA said:


> The generic "_*Rule-of-Thumb*_" for 'tweeking' spark plug gaps (from OEM number) is:
> 
> • *SMALLER* gap for *HP*.
> • *WIDER *gap for *MPG*.
> ...


I was thinking about this earlier, and it's a topic I'm still thinking about. The engine does run significantly more smoothly with .035" gaps than it does at .033" or .030". My thought was that the larger gap is what provides the more complete burn. 

I do have one thought that I'd like to throw out there. Detonation is caused by the ignition of fuel outside the ignition created by the spark, using fuel that was not completely burned by the initial combustion. Would it not then make sense that by adjusting our spark plug gaps, we could reduce the likelihood of knock, and therefore improve efficiency and fuel economy? I wonder if this has anything to do with the smoother engine acceleration and significantly improved throttle response while using the .035" spark plug gap.


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## bryanakron40 (Nov 8, 2012)

I set mine to .032" earlier today. The main reason for need a smaller gap on a turbo car is to keep the spark blowout from happening along with not over stressing the coils. My omni has run into this a couple times while trying to find out what gap works well. I have a holset from a 5.9 cummins on a 2.2 dodge 4 cyl. so finding the gap was a necessity to keep from blowing it out.


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## Greasemonkey2012 (Jul 8, 2012)

For trifecta tune what's the gap for 1.4t 


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## XtremeRevolution (Jan 19, 2012)

Greasemonkey2012 said:


> For trifecta tune what's the gap for 1.4t
> 
> 
> Sent from my iPhone using AutoGuide.com App


.028", and keep an eye out for spark blowout. You may need to go to .027", but most here with the Trifecta tune are fine on .028".


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## ecw73 (Mar 17, 2011)

2011 LTZ RS 1.4T auto. Regapped to .035 and noticed significant improvement in power (no bogging at low speed), better throttle response and, maybe I'm imagining it, but smoother shifting. Well worth the 20 minutes of work. 


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## Smdqt (Sep 5, 2012)

2012 LT 1.4L. Gapped mine last night. 2 were @ .027 and 2 were @ .021. Regapped (cough....tried to.....cough) to .035 (more like .033 to 0.35 b\c I was scared shtless that I might break them). So far no noticable improvements  . Can't report on MPGs b\c I barely drive the car during the week. Performance feels the same.



ecw73 said:


> maybe I'm imagining it, but smoother shifting. Well worth the 20 minutes of work.


Althought spark plugs don't have anything to do with transmission, I did notice that in manual mode, shifting from 2nd to 3d became smoother (it used to jerk, but I shift @ 2.5 RPM on average). Odd but nice...


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## WhiteAndBright (Mar 4, 2013)

I know I am late posting on this thread but I have a little something to add for your graph.. One of my plugs was at 0.18"!!! When I pulled them to check them and re gap them this is what I found starting on the passenger side moving to the driver side.. # 1 0.018 #2 0.020 #3 0.020 #4 0.019 When I would be sitting at a stop light the idle was really rough and the rpm needle would move like crazy (I'm sure it was the computer trying to compensate for this) Now that I have re gapped to 0.035 it runs smoother than it did with 2 miles on it and with doing that along with the reso delete and tire psi change I have gone from 25-30mpg avg to an overall avg of just over 41mpg and my personal best is 49.2mpg, before all of this my personal best was 34.6mpg... I wish I would have known about this 25,000 miles ago as I would have saved so much in fuel cost over that time something that I think GM should reimburse me for.. I think it is GM and NGK's mess up (that has been proven) that has caused me to run a lower mpg and cost more expense over the first 25,000 miles when buying fuel.. Just a thought!!


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## XtremeRevolution (Jan 19, 2012)

WhiteAndBright said:


> I know I am late posting on this thread but I have a little something to add for your graph.. One of my plugs was at 0.18"!!! When I pulled them to check them and re gap them this is what I found starting on the passenger side moving to the driver side.. # 1 0.018 #2 0.020 #3 0.020 #4 0.019 When I would be sitting at a stop light the idle was really rough and the rpm needle would move like crazy (I'm sure it was the computer trying to compensate for this) Now that I have re gapped to 0.035 it runs smoother than it did with 2 miles on it and with doing that along with the reso delete and tire psi change I have gone from 25-30mpg avg to an overall avg of just over 41mpg and my personal best is 49.2mpg, before all of this my personal best was 34.6mpg... I wish I would have known about this 25,000 miles ago as I would have saved so much in fuel cost over that time something that I think GM should reimburse me for.. I think it is GM and NGK's mess up (that has been proven) that has caused me to run a lower mpg and cost more expense over the first 25,000 miles when buying fuel.. Just a thought!!


I'm glad you did this and saw your fuel economy improve. It just goes to show how much of a difference a higher gap makes on these cars. Unfortunately, you're one of many who ran into this issue, as you will see from the 125+ collective pages that we have in 3 large threads discussing this.


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## WhiteAndBright (Mar 4, 2013)

XtremeRevolution said:


> I'm glad you did this and saw your fuel economy improve. It just goes to show how much of a difference a higher gap makes on these cars. Unfortunately, you're one of many who ran into this issue, as you will see from the 125+ collective pages that we have in 3 large threads discussing this.


I know I read through all 51 pages of it yesterday and last night. I woke up at 3 am this morning with my laptop still on and still on this thread.. lol The sad thing is that I work at a Chevy/Cadillac dealership and I am taking all of these threads to our service manager and he has never heard any of these complaints.. I think GM should be more involved and start informing the dealers not having members of this thread taking the info to the service depts. and them learning that way.. My service manager has told me that he wants me to print off all of the info on any subject that I run across so that he will know what's going on when a customer brings their car in for these repairs.. Just goes to show you how far ahead of GM that WE are on THEIR own product!!


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## obermd (Mar 3, 2012)

WhiteAndBright said:


> I know I read through all 51 pages of it yesterday and last night. I woke up at 3 am this morning with my laptop still on and still on this thread.. lol The sad thing is that I work at a Chevy/Cadillac dealership and I am taking all of these threads to our service manager and he has never heard any of these complaints.. I think GM should be more involved and start informing the dealers not having members of this thread taking the info to the service depts. and them learning that way.. My service manager has told me that he wants me to print off all of the info on any subject that I run across so that he will know what's going on when a customer brings their car in for these repairs.. Just goes to show you how far ahead of GM that WE are on THEIR own product!!


Sounds like you work for a good service manager.


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## hectorcist (Mar 3, 2013)

Quick question guys..are the gaps an issue in the 2013 model? Or did Chevy address that already?


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## obermd (Mar 3, 2012)

hectorcist said:


> Quick question guys..are the gaps an issue in the 2013 model? Or did Chevy address that already?


Unknown. We haven't had any independent measurements. GM claims they have fixed the issue.


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## UpstateNYBill (Jan 14, 2012)

I think everyone that bought a Cruze in the last part (or second half) of last year that checked their gap found it to be at factory spec. It wasn't alot of people, but it's a good sign.


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## WhiteAndBright (Mar 4, 2013)

obermd said:


> Sounds like you work for a good service manager.


He is very good, our dealership is very involved with General Motors and have reps and people from Detroit in all the time.. As long as we can stay one step ahead of the problems then we can assist the customer 110%.. I had the problem with my steering (notch or dead spot in steering) I had it fixed and since then we have had a few customers come in stating the same problem. Of course standard process is that the tech drives it and says could not duplicate leaving the customer upset that we could not fix her problem, I asked if I could drive it to try and duplicate the problem I did and I got it to do the same thing that mine had done, we replaced all parts that were affected based on me duplicating the problem. GM had sent their rep to "investigate" the situation and stood behind me when I said that there was a problem.. I drive one of these cars everyday and have since the car was brand new with 1 mile (perk of working at a dealership) There are still good people that work at dealerships (I work in the sales side) that want to help every single customer, you just have to find them and be nice and talk to them with respect not come in yelling at us, we can help and can save you A LOT of money, stress, and hard ache..


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## XtremeRevolution (Jan 19, 2012)

WhiteAndBright said:


> He is very good, our dealership is very involved with General Motors and have reps and people from Detroit in all the time.. As long as we can stay one step ahead of the problems then we can assist the customer 110%.. I had the problem with my steering (notch or dead spot in steering) I had it fixed and since then we have had a few customers come in stating the same problem. Of course standard process is that the tech drives it and says could not duplicate leaving the customer upset that we could not fix her problem, I asked if I could drive it to try and duplicate the problem I did and I got it to do the same thing that mine had done, we replaced all parts that were affected based on me duplicating the problem. GM had sent their rep to "investigate" the situation and stood behind me when I said that there was a problem.. I drive one of these cars everyday and have since the car was brand new with 1 mile (perk of working at a dealership) There are still good people that work at dealership(I work in the sales side) that want to help every single customer, you just have to find them and be nice and talk to them with respect not come in yelling at us, we can help and can save you A LOT of money, stress, and hard ache..


So people can give you more business and commend you for your efforts, what dealership would this be? 

I have a mind to start a running list of recommended dealerships that have demonstrated exceptional customer service and technical competence.


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## WhiteAndBright (Mar 4, 2013)

XtremeRevolution said:


> So people can give you more business and commend you for your efforts, what dealership would this be?
> 
> I have a mind to start a running list of recommended dealerships that have demonstrated exceptional customer service and technical competence.


Lake Country Chevy & Cadillac in Muskogee, Ok (suburb of Tulsa, Ok) I don't actually sell but I work in sales. When a customer comes in and buys a brand new Chevy or Cadillac (or certified used) I will sit in the car with them before they leave show them how every single option works, button does, pair their cell phones, setup their remote link app on their phones, connect their OnStar and answer any questions that they may have. If I don't know the answer to a question I have many people throughout General Motors that I can call to get the answer my thought is 100% of the customers get 100% of the questions they asked answered 100% of the time!! I go to tons of General Motor meetings, Ride and Drives of new cars that are coming out, auto shows, press releases, and take an ungodly amount of training test online for GM.. I am considered the "Technology Expert" per GM and their training courses for our dealership.. Our csi at the dealership last time I checked was 3.96 out of 4.00 for a 12 month rolling avg. that is borderline perfect. We take pride in caring for our customers!!


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## rb343 (Mar 18, 2013)

I have a 2013 Eco, just picked it up Saturday, 230 miles on it, build date 8/2012. I pulled the plugs and all were at .025. I changed them to .032. If it gets me an extra .5 MPG then it was worth it. At least mine were all gapped consistently.


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## XtremeRevolution (Jan 19, 2012)

rb343 said:


> I have a 2013 Eco, just picked it up Saturday, 230 miles on it, build date 8/2012. I pulled the plugs and all were at .025. I changed them to .032. If it gets me an extra .5 MPG then it was worth it. At least mine were all gapped consistently.


I get the impression that they fixed the consistency issue, and the plugs are in the middle of their new recommendation. Kudos to GM for knocking this problem off the list.


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## JordanNaylor (Feb 3, 2013)

Is the low fuel economy the only issue this causes? my 1.6 runs very choppy alot of the time, could this be to do with a spark plug gap? I don't know why its doing it though :/


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## jblackburn (Apr 14, 2012)

JordanNaylor said:


> Is the low fuel economy the only issue this causes? my 1.6 runs very choppy a lot of the time, could this be to do with a spark plug gap? I don't know why its doing it though :/


No; my 1.4 ran terrible and was super laggy, especially in the summer. Gaps did make a big change for me, as did using higher octane.

Then again, mine's a turbo, and turbo engines run much differently than NA's.

I'm not sure what the gap is supposed to be for the 1.6L, but it's worth pulling the plugs out and seeing if the gaps are consistent. Maybe you can ask your service dept for the specs and gap them yourself.


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## Peter2020 (Apr 8, 2013)

2012 Chevy Cruze LTZ gaps from driver side to passenger .019 .020 . 022 .018 gapped all of them to .035 Boy what a difference it makes !!! Much apprecciated to everyone in this forum !!


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## cruze01 (Mar 25, 2011)

XtremeRevolution said:


> I get the impression that they fixed the consistency issue, and the plugs are in the middle of their new recommendation. Kudos to GM for knocking this problem off the list.


Confirmed! I checked my 2013 RSLT yesterday, they were 28-28-28.5-28.75. Pretty darn close! I left them as is.....


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## ChevyMgr (Oct 27, 2010)

I'm sorry that I don't have the time nor will to read all 53 pages of this thread but what are we saying the gap is supposed to be. GM service manual says .028 on the 1.4L, 1.6L and 1.8L and if the spec was different before, what was it?


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## obermd (Mar 3, 2012)

ChevyMgr said:


> I'm sorry that I don't have the time nor will to read all 53 pages of this thread but what are we saying the gap is supposed to be. GM service manual says .028 on the 1.4L, 1.6L and 1.8L and if the spec was different before, what was it?


The original specs were:

1.8L 0.028" (no change)
1.4T 0.033 - 0.037"

You can see GM's response to Andrei about the spark plug gap issue at http://www.cruzetalk.com/forum/10-e...cial-statement-regarding-spark-plug-gaps.html.


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## ChevyMgr (Oct 27, 2010)

obermd said:


> The original specs were:
> 
> 1.8L 0.028" (no change)
> 1.4T 0.033 - 0.037"
> ...


Thanks.


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## Vetterin (Mar 27, 2011)

I replace my plugs about a month ago with Autolite iridium xp's gapped to .035 and have been noticing a flutter (for lack of a better term) while accelerating after about 2500 rpm. Last night I re-gapped to .028 and the smoothness has returned. It seems as though the sweet spot for MY car is between .028 and .032.


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## Lovedrop (May 7, 2013)

Will be doing this shoon, read all 53 pages... Can't wait to see what my 2012 6spd manual sparks plugs length are!


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## jesse (May 10, 2013)

The gapping issue has not been corrected for all 2013's. Pulled mine today from a 1.4T, all below .020!! My gapping tool only went to .020 so I couldn't get an exact measurement but it wasn't even close. Fixed the rough idle issue, good thing there is only 500 km on it


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## 70AARCUDA (Nov 14, 2010)

jesse said:


> *The gapping issue has not been corrected for all 2013's.* Pulled mine today from a 1.4T, *all below .020!! *My gapping tool only went to .020 so I couldn't get an exact measurement but it wasn't even close. Fixed the rough idle issue, good thing there is only 500 km on it


It is totally_ pathetic _that GM cannot-or-has not "fixed" this problem *yet*?!?!?

Come on GM, you've *known* about this undersized & sporatic "gap" problem since 2012!


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## Oh Negative Black & Green (May 17, 2013)

Hopefully I can talk my salesman into getting it done free... not likely but worth a try (especially if it's a factory goof on their part.)


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## DrVino (Jun 20, 2013)

Checked mine this morning (2011 LT). All four NGK IFR7X7G plugs had gaps of ~0.026 to 0.027 and were in excellent condition (now through 39,000 kms - surprized given the deep cold winter starts with no pan heater). I have gauge loops for 0.025 and 0.028, so these are estimates since the former loop could clear through while the later loop couldn't quite make it that easily. Wouldn't want to risk snapping that tiny iridium electrode, I left them as is, given they are close enough to that ideal 28mil. A little bit of dielectric grease inside the boots and it was a piece of cake getting the assembly back together.


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## peejoe (Dec 21, 2013)

I am thinking that this is a co-incidence but after I gapped my plugs to .038 I got lots of performance for a bit then on the take off I got hesitation and then the check engine light started flashing .. I panicked and pulled into my driveway and called roadside assistance .. they took the car to the chev dealer and under warranty changed the coil assembly.... now i still have the performance but i still get that little bit of hesitation once in a while .. maybe i have to gap a little bit smaller .. and just maybe the coil assembly was on its way out anyway.... its got 44000 miles on it .. 2011 eco 1.4t


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## obermd (Mar 3, 2012)

0.038 is the absolute upper end on the plugs. You will start to see spark blowout at this point.


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## jblackburn (Apr 14, 2012)

^What he said. I had blowout when my gaps got to around .038" as well. Close that gap down to .030" or so - it will grow with time.


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## SneakerFix (Jul 28, 2013)

That coil pack should have lasted longer then 44k. I think they just replaced it just to "fix" the issue of the hesitation. But like the rest said .38 is to much. .30 is where I'm gapped at now with no tune or performance parts. 40+ MPG on a turbo that won't hold boost


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## iggy (Feb 14, 2013)

I checked my gap on my 2013 Cruze LTZ, 1.4L Turbo. 3 our of 4 plugs were just under .025", one was just over .025". I re-gaped them all to .036.

I can't say as I see any huge differences in the way the car runs. It might possibly have a little less lag from a dead stop, and maybe gets slightly better gas millage ( certainly not any worse ). If I am seeing any real difference in MPG, it's probably 2% or so. ( went from 35.4 to 36.1 MPG in my daily driving, which is about 70% high way (70MPH ) , 25% two lane blacktop rural hwy (45 to 55 MPH), 5% small city driving (very few jack rabbit starts or stops) ).

For GM to 'fix' the problem of the GAP not being right, I suspect they'd have to get the spark plug maker to 'fix' the problem. I highly doubt that anyone at GM is going to be re-gaping mass quantities of plugs. Also, the 2013 Cruze owners manual still lists .028" gap for all engines. Meanwhile the average person owning a cruze would likely never notice a difference between having their plugs at .025" vs .035".


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## obermd (Mar 3, 2012)

iggy said:


> I checked my gap on my 2013 Cruze LTZ, 1.4L Turbo. 3 our of 4 plugs were just under .025", one was just over .025". I re-gaped them all to .036.
> 
> I can't say as I see any huge differences in the way the car runs. It might possibly have a little less lag from a dead stop, and maybe gets slightly better gas millage ( certainly not any worse ). If I am seeing any real difference in MPG, it's probably 2% or so. ( went from 35.4 to 36.1 MPG in my daily driving, which is about 70% high way (70MPH ) , 25% two lane blacktop rural hwy (45 to 55 MPH), 5% small city driving (very few jack rabbit starts or stops) ).
> 
> For GM to 'fix' the problem of the GAP not being right, I suspect they'd have to get the spark plug maker to 'fix' the problem. I highly doubt that anyone at GM is going to be re-gaping mass quantities of plugs. Also, the 2013 Cruze owners manual still lists .028" gap for all engines. Meanwhile the average person owning a cruze would likely never notice a difference between having their plugs at .025" vs .035".


Take a look at my first post in http://www.cruzetalk.com/forum/34-1-4l-turbo/46833-new-copper-spark-plugs.html. I did some computations on my OEM plugs when I pulled them and figured out why GM came back with 0.025-0.028" for the plug gap when installing them.


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## hificruzer226 (Mar 27, 2013)

When I checked mine earlier when this thread started pumping my 13 eco m/t all read .028" .... all 8 of them 





just kidding all 4


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## mullymull40 (Aug 23, 2014)

The owners manual calls for 0.028 gap for both 1.4L & 1.8L.


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## obermd (Mar 3, 2012)

mullymull40 said:


> The owners manual calls for 0.028 gap for both 1.4L & 1.8L.


For the 2013 and later model years, and the footnote states this is for replacement plugs only. For 2011-2013 the 1.4T was listed at 0.033 to 0.037 inch. This is also what was in GM Global Connect.


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## turbobob_01 (Mar 20, 2013)

Just read all 55 pages of this. My car has 118k miles. Guess I will set my new plugs at .035. Never expected to read so much on the subject of plug gap.


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## wasney (Mar 3, 2015)

lol yea I have read through this before too. If you buy copper replacements then gap them at .28. I recommend them, they seem to make the car drive better.


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