# Bucking, Hesitation and Poor Economy Fix - Cleaned EGR and Intake (throttle) Valve



## Niebs6.2 (Feb 8, 2014)

Hello Everyone. I have been a following member for quite a while and have found the information in this forum very helpful. I have a 2014 CTD that i purchased in September 2013. I drive mixed 80/20 highway/city. I maintain the car well and its been very reliable for me, but I have experienced a few issues that i have been able to relate to on this site. Bucking (mild and severe) after coasting or light throttle, and a huge lag (almost a stumble) when hot in start/stop situations. I've also experienced several random hard downshifts. These problems first occurred when the car was about 1 year old (not that bad or often) and they seemed to improve after the first emissions recall. Shortly after the latest recall, the symptoms reappeared and gradually became worse.

Background/history: 
107,000km
O2 Sensor replaced for P026C code - Mid 2015
DEF Tank Heater - Aug 2016
Emission Recall 15594 - Ran great after recall, but still got occasional P026C code
Emission Recall 17089 - Above mentioned symptoms re-appeared and gradually got worse

Two posts caught my attention: 15 cruze won't start or run, and Help diagnose bucking during regens. Since reading these posts, i have cleaned my EGR valve and the intake valve (throttle plate). Thank-you IndyDiesel for the write-up on cleaning your EGR valve - it went well, just as you described it. I did not replace the gasket plate but probably will if I service the EGR valve again. There is coolant behind the gasket plate and if you have any pressure in the cooling system, it will drip while the EGR valve is out (i had a small panic when i saw this). I have attached four pictures below. 1.) Location of EGR and gasket plate 2.) Intake pipe removed looking into throttle body 3.) close-up of the very gummed up throttle valve 4.) valve body after cleaning

I did the EGR first, about 5 days before i cleaned the throttle body. I noticed a significant improvement in fuel economy and acceleration. The valve was not stuck open, but it was not moving very free and it would sometimes bind up. I used brake clean and worked the valve back and forth with an attached vise-grip. I was pleased with the improvement in performance, but the car was still bucking, mostly first thing in the morning. 

When I removed the intake pipe at the throttle body i pushed the plate closed with my finger and it did not release on its own spring tension, but would pop free after a second or so. I figured this could be the cause of the bucking. Cleaning this was much more challenging. I used throttle body cleaner sprayed on rags and a small plastic scrapper to do most of the cleaning. Since so much crap was falling down onto the bottom of the intake (just on the bottom where i could still see it) , i rigged up a small plastic hose (about 3/8 inch) connected to my shop vac to suck out all the carbon debris. What a mess in there - really disappointed to see. I think i could have removed the whole throttle body assembly as well which would make this much easier and allow access to clean further into the intake. Care should be taken to not spray any cleaners directly into the intake since any residual solvents would ignite and combust very different than diesel fuel, potentially causing significant engine damage.

So not sure why my intake got so gummed up. Are there any other reports on this? I've always used the proper engine oil and my UOAs have looked very good. I drive a lot of highway miles, but i could be a bit light on the throttle. All that stuff had to come through the PCV, so I may have to look at that further (catch can....ect.). I also find it interesting these symptoms came back after the latest emissions recall. I will be keeping an eye on the intake valve for sure. The car is running great again with fuel economy back up to near the best i've ever seen, and the bucking is gone, even during the regen it did today. I sure love this little car and hope this helps anyone having similar issues.


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## Blasirl (Mar 31, 2015)

Niebs6.2 said:


> Hello Everyone. I have been a following member for quite a while and have found the information in this forum very helpful. I have a 2014 CTD that i purchased in September 2013. I drive mixed 80/20 highway/city. I maintain the car well and its been very reliable for me, but I have experienced a few issues that i have been able to relate to on this site. Bucking (mild and severe) after coasting or light throttle, and a huge lag (almost a stumble) when hot in start/stop situations. I've also experienced several random hard downshifts. These problems first occurred when the car was about 1 year old (not that bad or often) and they seemed to improve after the first emissions recall. Shortly after the latest recall, the symptoms reappeared and gradually became worse.
> 
> Background/history:
> 107,000km
> ...


Welcome Aboard!:welcome:

With your first write-up done as well as that, I look forward to some How-To's and other exposes' as well from you!

Don't forget to introduce yourself and your Cruze here.

EDIT: Fix your pic's!


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## AlbertaDiesel (Aug 30, 2017)

Wow - that makes me think the delete might be the way to go for sure...


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## Niebs6.2 (Feb 8, 2014)

Thanks - I think I fixed the pic's


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## Rivergoer (Mar 30, 2017)

Wow, had no idea the INTAKE side would be subject to so much fouling. Would expect the exhaust side to look like that but not the Throttle Body.

Excellent write up and thanks for including the pictures!


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## Taxman (Aug 10, 2017)

EGR has been doing that to Mercedes diesel intakes for the past 30 years. My 1979 was the last year for a turbo without EGR, my newer cars have had their EGRs disabled. 

I hoped the latest common rail systems wouldn't be as sooty, but apparently that was wishful thinking. 
If I had a CTD, I'd clean the intake and put a tune in it that doesn't open the EGR valve.


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## MP81 (Jul 20, 2015)

Thinking I may try tackling this today (if its not raining), prior to our trip up north tomorrow. I'll probably just remove the throttle valve, though. That way I don't have to worry about what I use, and all the crap I cleaned out.


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## Niebs6.2 (Feb 8, 2014)

MP81 said:


> Thinking I may try tackling this today (if its not raining), prior to our trip up north tomorrow. I'll probably just remove the throttle valve, though. That way I don't have to worry about what I use, and all the crap I cleaned out.


Good call. Curious how your intake looks. Great time to do this before a long trip!


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## MP81 (Jul 20, 2015)

Niebs6.2 said:


> Good call. Curious how your intake looks. Great time to do this before a long trip!


For sure - especially with so much freeway. I've noticed that it really hasn't been _as_ great on the freeway as it used to be. I'm hoping this is all related.


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## IndyDiesel (May 24, 2015)

With my car being for last 25k miles being almost all highway miles, I am coming to the conclusion that driving our diesels hard on a regular basis might help. So the old saying drive it like you stole it might help more than I thought. The easiest way to do it is to run for a mile or two at 4000 rpm with the transmission in manual mode, maybe once a week. I think it could help, when dealer does a manual regen it is at 3000 rpm for an extended period of time, so I can't imagine 4000 rpm for a couple min would harm anything.


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## MP81 (Jul 20, 2015)

For the last few years, the majority of tanks are 80-100% city, for what it's worth.


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## Niebs6.2 (Feb 8, 2014)

IndyDiesel said:


> With my car being for last 25k miles being almost all highway miles, I am coming to the conclusion that driving our diesels hard on a regular basis might help. So the old saying drive it like you stole it might help more than I thought. The easiest way to do it is to run for a mile or two at 4000 rpm with the transmission in manual mode, maybe once a week. I think it could help, when dealer does a manual regen it is at 3000 rpm for an extended period of time, so I can't imagine 4000 rpm for a couple min would harm anything.


Agree - About a week before I cleaned my EGR valve, I tried running the car harder than normal. I was keeping the trans in manual gear 6 and letting the engine run full load up some moderate hills, letting off once I was too far over the speed limit. After a week of this I was seeing higher peak boost values. I think at full throttle full load, the EGR should be closed? So repeating this may have started to free up the valve. I took the EGR valve off as the performance was still inconsistent.
High RPM may be effective too, but it's hard to keep the engine at a full load at 3500rpm. The 2.0 CTD does not seem to be lugging in 6th gear at full throttle. I will make a habit of this on my drive home when possible.


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## boraz (Aug 29, 2013)

IndyDiesel said:


> With my car being for last 25k miles being almost all highway miles, I am coming to the conclusion that driving our diesels hard on a regular basis might help. So the old saying drive it like you stole it might help more than I thought. The easiest way to do it is to run for a mile or two at 4000 rpm with the transmission in manual mode, maybe once a week. I think it could help, when dealer does a manual regen it is at 3000 rpm for an extended period of time, so I can't imagine 4000 rpm for a couple min would harm anything.


theres a 8 mile 10% hill on my way to work, 4000+ engine braking down the hill, 4000+ lower gear up the hill, every time


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## MP81 (Jul 20, 2015)

boraz said:


> theres a 8 mile 10% hill on my way to work, 4000+ engine braking down the hill, 4000+ lower gear up the hill, every time


That's what I miss about not driving to North Carolina anymore (in-laws moved to Atlanta) is driving on I-77/I-64 through the Appalachians. 

Full decel-fuel-cut, engine braking down that grade while going 70 was a blast!


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## Rivergoer (Mar 30, 2017)

I do a lot of easy 60 mph highway, wondering now if at 70K miles my intake may be gumming up too. 

Are you all saying the 4000 rpm "drive it like u stole it" every once in awhile wil clean a dirty throttle body or just help keep it from gunking up AFTER it's been physically cleaned?


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## Diesel Dan (May 18, 2013)

Just the nature of the beast, EGR that is.
I'm not surprised and pretty much expected to see this. Just like the old MB diesels the light duty 6.2 and 6.5L V8 engines that have egr gum up the intakes. What's new is the throttle valves, coolers and sensors. 

To the OP, nice post and my t/v, egr is on the list for sure.


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## boraz (Aug 29, 2013)

Rivergoer said:


> I do a lot of easy 60 mph highway, wondering now if at 70K miles my intake may be gumming up too.
> 
> Are you all saying the 4000 rpm "drive it like u stole it" every once in awhile wil clean a dirty throttle body or just help keep it from gunking up AFTER it's been physically cleaned?


i cant see how it would clean a dirty one.

when wife brings car back after the weekend im gonna have a look at my egr and throttle plate


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## raffmanlt (Oct 4, 2014)

I need to look at mine also. Wow


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## jwarcop (Aug 18, 2013)

Sounds like this has been my problem all along. Two dealerships have tried working on this problem and neither have ever mentioned this.


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## TheRealHip (Sep 1, 2014)

I wonder if you can just block off the egr valve?


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## MP81 (Jul 20, 2015)

TheRealHip said:


> I wonder if you can just block off the egr valve?


If you are deleted, you absolutely can.


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## oreo382 (Sep 17, 2014)

Cleaned my throttle body,egr and maf sensor.Small improvement in cold start sputtering but far from a fix.There is something else going on with these cars.Mine has 36,000 miles on it.Has been doing this since about the time I got the latest nox sensor/reprogram done.


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## oreo382 (Sep 17, 2014)

Niebs6.2---You quoted " I was pleased with the improvement in performance, but the car was still bucking, mostly first thing in the morning. " My car was doing the same even after cleaning the MAF,EGR and throttle body.Dealer finally figured out with the help from GM that the intake valves were caked with carbon.The fix is to remove the head and clean/recondition it along with cleaning the intake manifold (that part i'm assuming but the head is for sure).Mine was doing exactly what you describe,first morning start,stumbling and missing,worst when you first put it in reverse or drive and sit there with the brakes on.Fuel mileage was slowly getting worse,stumbling etc. goes away when engine warms up and runs smooth.No check engine light but dealer said they logged multiple misfire codes with their scanner,i guess those codes are stored but no check engine light.My cheap code scanner did not show anything.


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## Niebs6.2 (Feb 8, 2014)

oreo382 said:


> Niebs6.2---You quoted " I was pleased with the improvement in performance, but the car was still bucking, mostly first thing in the morning. " My car was doing the same even after cleaning the MAF,EGR and throttle body.Dealer finally figured out with the help from GM that the intake valves were caked with carbon.The fix is to remove the head and clean/recondition it along with cleaning the intake manifold (that part i'm assuming but the head is for sure).Mine was doing exactly what you describe,first morning start,stumbling and missing,worst when you first put it in reverse or drive and sit there with the brakes on.Fuel mileage was slowly getting worse,stumbling etc. goes away when engine warms up and runs smooth.No check engine light but dealer said they logged multiple misfire codes with their scanner,i guess those codes are stored but no check engine light.My cheap code scanner did not show anything.


Hey oreo382,
I've been following along on this topic since my initial post as my problem has returned. It has been getting pretty bad the last couple months. I've actually had it stall on me and when i went to crank it over, it sounded like it had poor compression - i suspect this is from bits of carbon breaking off and preventing a seal around the valve seat. So to me, your diagnosis makes sense. Too bad its such a big job (probably expensive too). Any suggestions on an intermediate fix ?


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## oreo382 (Sep 17, 2014)

GM has some kind of system where they spray cleaner into the intake,let it sit for a couple hours then put some stuff in the gas tank.Not sure if thats just for gas engines though.I'd be scared to hydrolock the engine doing that.They say if no improvement do it a second time.Sounds like a bandaid or for lightly carboned engines at best.My dealership went straight for removal of the head,not sure if the put a scope in the intake before coming up with removing and cleaning.GM may have suggested removal right off.I may get it back this week and i'll try and find out the cost.I see you have about 60K miles,80% highway driving.I have 40K miles,mostly city.Do you live in a cold climate area like I do (Winnipeg,Canada)?
I'd like to know what that 2nd emission reflash actually entailed.


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## MP81 (Jul 20, 2015)

Sounds like Seafoam. 

**** takes _all sorts_ of carbon buildup off, and makes your vehicle appear that it is on fire when you go for a "spirited" drive after.

Should still work for a diesel, I'd think, as you suck it in through a vacuum hose. But yours may very well have been past what could have been removed even by Seafoam.


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## BDCCruze (Jul 12, 2017)

A dealer near me sells BG Diesel Induction service that says to:

Cleans EGR valve and passages
Cleans plenum and air intake
It sounds promising but I'm afraid that the car is running fine now and I don't want to cause problems.


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## oreo382 (Sep 17, 2014)

BDCCruze said:


> BG Diesel Induction servi





BDCCruze said:


> A dealer near me sells BG Diesel Induction service that says to:
> 
> Cleans EGR valve and passages
> Cleans plenum and air intake
> It sounds promising but I'm afraid that the car is running fine now and I don't want to cause problems.


That BG system is like the one GM uses.They don't specifically say intake valves,makes me wonder how effective it is.In my case GM said r and r the head,no mention of using this method.


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## oreo382 (Sep 17, 2014)

Update----Dealer called to say car was fixed.Picked it up and had check engine light immediately.Wheeled back in and told service advisor.He quizzed the mechanics and they said,oh yeah,one of the glow plugs is defective,its on order and will call you when its in.Due to warm weather its ok to drive.With that went on my way for a short highway drive.Pulled into the condo parking spot and pulled the engine cover to see if they broke off the glow plug,was greeted by a hissing sound coming from the injector area.Closer inspection revealed fuel leaking out and bubbling in the fuel injector well in the head.Back to the dealer,checked by them and confirmed,no driving due to safety hazard.Will have to order a new one.The saga continues.In addition I asked the advisor what the cost was so far.He said the cost he has is lower than what someone would pay out of pocket.Dealers cost $2400.00,he said at least $3500.00 for a regular customer.


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## TheRealHip (Sep 1, 2014)

They charged you $2400??


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## oreo382 (Sep 17, 2014)

TheRealHip said:


> They charged you $2400??


No its all warranty work.That number is what the dealership charges back to GM for the work,for parts and labor.As I said the advisor said if a person had to do this not under warranty it would have cost them around $3500.00.So it seems that due to EGR mixed with PCV gasses and city driving is death to these cars.Not to mention most diesel fuel that has low cetane and no Top Tier cleaners. Its too bad,when I bought it what won me over was the engine,torquey,felt like driving a big V8,nice quiet ride,felt like a much bigger car.It looks like this diesel isn't the only one with carbon problems,lots of GDI gas engines with this problem.Some have gone to dual injection systems to try and stop the issue,Toyota for one.


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## plano-doug (Jul 1, 2015)

oreo382 said:


> It looks like this diesel isn't the only one with carbon problems,lots of GDI gas engines with this problem.Some have gone to dual injection systems to try and stop the issue,Toyota for one.


That brings up an interesting question: how have diesel engines dealt with this all along? GDI is new, but diesels have always been DI ; how have they avoided carbon buildup on the valves? 

Sorry if that's rhetorical, but maybe there's something to borrow for the gas engines.

Doug

.


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## oreo382 (Sep 17, 2014)

plano-doug said:


> That brings up an interesting question: how have diesel engines dealt with this all along? GDI is new, but diesels have always been DI ; how have they avoided carbon buildup on the valves?
> 
> Sorry if that's rhetorical, but maybe there's something to borrow for the gas engines.
> 
> ...


There are past diesels that have carbon problems,mercedes comes to mind and I think some Volkswagens and maybe others.Emissions equipment,bad engineering,fuel that hasn't kept up with these issues.They are now getting into top tier diesel fuel like they did with gasoline.Gas engines were carboning the valves even with port fuel injection due to lack of cleaners in the fuel.Time for oil companies to step up and give the U.S. and Canada higher quality Ie: higher cetane and top tier diesel countrywide.


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## everett33 (Aug 1, 2018)

After reading through this thread, I decided to clean my throttle valve because I had noticed the slight bucking at low speeds like in parking lots over the past four months. Three months ago I had to have my Cruze towed to a shop because it would crank and start but not run for more than a second. The shop replaced the EGR valve becasue it had become stuck due to the carbon buildup and would not let the engine run.

Now that I have seen first-hand what the EGR and valve train vent are doing to my intake, I want to put a stop to it. I have seen links to the Oz tuner and KermaTDI tuner and am a little confused about what each are capable of. Currently I have a bone stock (besides cosmetics) diesel that I want to delete while keeping the power gains in a safe range and the sound level near stock. What are my options?

Edit: 82,000 miles with unknown history before July 2018 when I purchased it from its second owner.


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## oreo382 (Sep 17, 2014)

That first picture should be enough to convince anyone to get rid of the egr.Brutal,you should send that picture to Chevrolet,not that they will do anything.BTW,how does it run when you first start it after sitting overnite and put it in gear? Does it stumble and miss?


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## sailurman (Sep 29, 2016)

Ugly, but cleanable/repairable for both at little cost right. How many cleans would it take to recoup the $1200+ you will throw away in the delete/tune on a car that already has close to 100K Miles. A little bit of maintenance every couple of years. But the DEF reservoir itself costs $500 plus you say. I replaced it myself for less than $200 in less than an hour. If you are marginally mechanically inclined this should be a no brainer if you are not looking for the performance boost (which you can get with just a tune at less than half the cost. I won't even go into the environmental footprint (though so small some might say ) . These of course are my personal opinions.


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## everett33 (Aug 1, 2018)

oreo382 said:


> That first picture should be enough to convince anyone to get rid of the egr.Brutal,you should send that picture to Chevrolet,not that they will do anything.BTW,how does it run when you first start it after sitting overnite and put it in gear? Does it stumble and miss?


The car ran perfect before the cleaning. No hesitation when starting or driving, not even in the negative temperatures last winter here in Michigan.


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## kelaog (Aug 1, 2019)

MP81 said:


> If you are deleted, you absolutely can.


I would recommend just having the map 0'd and leaving it in place. It will be closed 100% of the time anyways so removing it adds no benefit to the existing delete/tune. It does however benefit the manufacturer of the block off plates 

I had a Smart fortwo diesel once, and I debated removing the EGR. Fortunately there was a long cool run of piping between the EGR and the engine that, if you were lucky, would clog up before the EGR valve did. It was said if you hit 50,000 km without the CEL going on for the EGR then it never would because the car deleted its self upstream haha. I removed one end of the pipe to verify, it was indeed plugged solid but the valve still moved freely which convinced the car all was well.


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## pacolino (Aug 1, 2015)

I guess I'm up to cleanup my EGR and the throttle valve as my car starts hard in the morning and it has really poor mpg and more regens (mileage now is 163,000km).
Does anyone know the torque values for EGR and throttle valve bolts? Thanks.


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## 2014 Encore (5 mo ago)

That BG service is known to erode turbo bearings.


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## pacolino (Aug 1, 2015)

does anybody know the torque figures for EGR and throttle valve bolts?


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## MP81 (Jul 20, 2015)

89 in-lb


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## pacolino (Aug 1, 2015)

MP81 said:


> 89 in-lb


for both, egr and throttle valve?


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## MP81 (Jul 20, 2015)

pacolino said:


> for both, egr and throttle valve?


Yup! The throttle valve is a straight torque, the EGR had another step in there, like 51 in-lb then 89 in-lb. Given how small the torque is, that's kind of surprising they even bother.


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## BDCCruze (Jul 12, 2017)

MP81 said:


> Yup! The throttle valve is a straight torque, the EGR had another step in there, like 51 in-lb then 89 in-lb. Given how small the torque is, that's kind of surprising they even bother.


So that you neither under torque OR _over torque_.


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## MP81 (Jul 20, 2015)

BDCCruze said:


> So that you neither under torque OR _over torque_.


Sure, but when it comes to that low of torque, it is rare to see. Especially when you look at other parts with the same torque spec not needing it. 

But it's likely to make sure it settles down on the seal evenly.


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