# '17 Rough Idle Help Please



## 93bandit (Mar 2, 2020)

I have noticed this rough, stumble idle in my 17 Cruze as well. It's done it since it was new, and I have 44k on it currently. My dad bought a 17 Cruze as well and has about 55k on it, and his has a similar random stumble in the idle as well. Sometimes you can feel the car shake when the idle stumbles. It's most noticeable when the engine is at operating temp. Otherwise, performance in both of our vehicles is great. Good fuel economy, good power, no CEL, no oil consumption or other symptoms. My car has a manual trans, my dads has the auto. We both run 87 octane. Being that mine is manual, I shift so that it doesn't lug. My dad just drives his auto normally, and doesn't force downshifts when it lugs (that I'm aware of). 

No one has replied to the OP. Are we three the only ones with this issue? I'm fairly certain it's not a piston failure issue, as there are no other symptoms. I've searched this forum and read countless threads, but most of them are related to piston failure. 

I've considered spark plugs, but both of our vehicles have done this since new so I doubt it's a maintenance issue. I haven't taken it to the dealer for this, but I'm certain the either wouldn't notice, or they'd say it's characteristic of the design.


----------



## Fireworks234 (Jan 4, 2018)

The biggest thing is that these cars do not like 87 octane. Try upping the octane and see if performance improves. I know from experience that these cars seem to run a bit smoother when running higher octane. Give it a couple of tanks or at least an empty tank filled up with higher octane before saying this hasn't helped. 

On a side note, you could try pulling the spark plugs and checking the gap as on my '16 that I had, all of the gaps were all over the place. I know they say they're "Pre-gapped" and not to be messed with but man mine were all over the place.


----------



## 93bandit (Mar 2, 2020)

I'll check plug gap today, and may even just replace them. They're cheap. 

As for fuel octane, I live in Michigan and our temps are normally fairly cool so I've been hoping 87 would be sufficient, I've only heard SPI once at highway speeds when I went WOT in 6th gear. I immediately let off when I heard it. My normal commute is 108 miles per day and I drive it gently so I've been trying to get by on 87. I've got nearly a full tank right now, and I haven't been driving much due to the current virus situation, but I intend on trying 91 octane once it's time to fill up. What better time to experiment than now with gas prices so low? I have considered trying 89, but I suspect I wouldn't notice much of a difference. I have also considered using 89 through the cooler months and 91 in the summer.


----------



## 93bandit (Mar 2, 2020)

What about carbon buildup in the intake and on the intake valves? That could cause rough idle. I've considered running some cleaner through it, but I don't want to harm the cat.


----------



## Iamantman (Sep 24, 2018)

93bandit said:


> What about carbon buildup in the intake and on the intake valves? That could cause rough idle. I've considered running some cleaner through it, but I don't want to harm the cat.


Not at 20k. That engine should look brand new unless it's been abused. In general those injector cleaners are snake oil unless used regularly and even then the difference is negligible and mainly to justify to the fact that someone isn't using good quality gas with the proper additives. 

If you really wanted to clean your injectors because you thought there was an issue, you would remove them from the car and do a bench test and cleaning.


----------



## 93bandit (Mar 2, 2020)

Iamantman said:


> Not at 20k. That engine should look brand new unless it's been abused. In general those injector cleaners are snake oil unless used regularly and even then the difference is negligible and mainly to justify to the fact that someone isn't using good quality gas with the proper additives.
> 
> If you really wanted to clean your injectors because you thought there was an issue, you would remove them from the car and do a bench test and cleaning.


My car has 44k. Also, I don't want to clean my injectors, I was asking about intake runner and intake valve cleaners. You know, you would put through the intake post MAF to clean the carbon buildup from the intake runners and valves in the head. I have a Gen2 Cruze with the LE2 which has direct injection. High quality gas will have no affect on carbon buildup in the intake because there is no fuel washing the intake valves. I always use top tier fuel anyways.


----------



## Iamantman (Sep 24, 2018)

@93bandit Oh yeah I gotcha. I was saying for the OP though, he's at 20k so I really doubt he's got build up to the point of it affecting his idle.

As for your car I've seen all of the seafoam videos. You've probably got to be near double where you are now with mileage for it to affect performance but a lot of folks want that peace of mind so they run that on their engine every once in a while. I really don't think it does much though. Even the before and after pics people take with scopes are kind of shoulder shrugging imo.

I think if you're worried about it a catch can would be a smarter route to take. I might actually go that route at some point as a side project.


----------



## 93bandit (Mar 2, 2020)

@lamantman I agree that the cleaners aren't always the most effective. However, I'm of the opinion that if you make it a point to add a cleaning into the maintenance routine at consistent intervals, it may help. 

But I agree, a catch can is likely a better option and I intend on adding one once my powertrain warranty expires.


----------



## Iamantman (Sep 24, 2018)

93bandit said:


> @lamantman I agree that the cleaners aren't always the most effective. However, I'm of the opinion that if you make it a point to add a cleaning into the maintenance routine at consistent intervals, it may help.
> 
> But I agree, a catch can is likely a better option and I intend on adding one once my powertrain warranty expires.


Yeah same. I'll probably add one the day my warranty is up just as a little added insurance.

I did a little digging though and it sounds like the answer might come in the future as simply improved motor oils with carbon fighting additives included. If they just aren't able to fight the physics of oil seeping past the valve seals, and PCV and EGR systems are necessary for environmental reasons, might as well make that oil less susceptible to carbon build up. I found this article on Valvoline's website that get's into it a little bit. https://team.valvoline.com/diy/truth-behind-carbon-buildup  Their new "Modern engines" oil was designed specifically for this issue.

Jason from Engineering Explained did a great overview of this actually here as well around the same time that they introduced their new oil. He's got a great channel and is always very clear and easy to understand.


----------



## 93bandit (Mar 2, 2020)

That's an interesting video. I've always been a bit of a skeptic though, as far as their 30% claims. Does that oil resist carbon buildup better than other oils? Maybe so, but is it THAT good? I don't know. It would take years to determine, and I'm willing to bet an intake cleaning would be necessary after so many miles regardless. Maybe it wouldn't be as severe, but who knows. Most of those claims come from controlled lab testing and are less effective in the real world.

Or... Would a catch can plus using this "modern" oil fix the problem??? I might have to perform an experiment. I have a bore scope, so maybe after my warranty is up at 60k miles, I'll peak inside to assess the current carbon build up. Take pictures, make notes, then install the catch can and switch to this oil and run it. I could probably take a peak inside every ~20k and see what it looks like.

Also, I filled up yesterday with 93 and went on a 150 mile trip to see how it runs. It seemed to run smoother, and I did a few WOT pulls in 5th and 6th from below 2k rpms and it didn't shutter. Normally it would, so I think 93 helped. I'll run a few more tanks and see how it behaves. I'll likely be switching to 93 as peace of mind anyways, regardless of performance.


----------



## Iamantman (Sep 24, 2018)

93bandit said:


> That's an interesting video. I've always been a bit of a skeptic though, as far as their 30% claims. Does that oil resist carbon buildup better than other oils? Maybe so, but is it THAT good? I don't know. It would take years to determine, and I'm willing to bet an intake cleaning would be necessary after so many miles regardless. Maybe it wouldn't be as severe, but who knows. Most of those claims come from controlled lab testing and are less effective in the real world.
> 
> Or... Would a catch can plus using this "modern" oil fix the problem??? I might have to perform an experiment. I have a bore scope, so maybe after my warranty is up at 60k miles, I'll peak inside to assess the current carbon build up. Take pictures, make notes, then install the catch can and switch to this oil and run it. I could probably take a peak inside every ~20k and see what it looks like.


Yeah that's what I'm thinking. I have no idea about that specific oil but oil tech will only get better over the years and with a catch can installed you'll be in about as good shape as you can be. Like you said though it will take a while (we're talking years here) for your experiment to give you anything in return and even then it will be an educated guess from a single use case. So in other words, not scientific at all. But the engineers are obviously aware of this issue, it's a cost vs. reliability issue in the end. Every car could have a system like that in place but think about how many engines would blow up because someone didn't empty their catch can? It would be a disaster so instead, you leave it alone and do some periodic cleaning until oil tech catches up? Besides, It's really not a big issue outside of the "enthusiast" community anyway so that's my educated guess anyway.


----------

