Rough idle in gear while stopped...

[Pirate Luke]

Rough idle in gear while stopped...SOLVED

EDIT:
I started this thread to request guidance/knowledge for my own idle issues after reading all the idle threads here and on google without success. After extensive research of various systems in our 1.4L turbo engine, I've come to the conclusion that this PCV system is something that every sonic owner needs to be educated about, and is likely an underlying cause to many of the sonics issues (rough idle, lower mpg, oil consumption, vacuum leaks, inability to hold boost, reduced engine life). So I'll attempt to make this thread as useful as possible to others that end up here for similar issues.
:banana:Read post 10 for the solution to my problem.:banana:


ORIGINAL POST:
So I have an idle issue that crept up a couple months ago that I'm attempting to chase down. Hoping for some of your inputs if any of you have experienced similar symptoms.

Car: 2013, 1.4L auto - 100k miles - no mods at all
This ONLY happens while IN GEAR and STOPPED. (This was only true in the first few months I noticed the issue, after time went on it got worse.)

Basically when in D, M, or R, and stopped for any period of time, the car will have rough vibrations and feel like it's trying to surge past the pressure I've applied on the brakes to go forward. In terms of how bad it is, about 50% of my passengers make a remark about it when stopped. On days where it seems worse than others, if I have my music up which dampens how much I notice it, sometimes it'll buck/surge just enough that I quickly check my rear view mirror because it felt like someone behind me slightly tapped my bumper.

Now on to things I've tried/correlated with the rough idle.
- I have changed and gapped new spark plugs, no difference.
- I bought another ignition coil just in case the one I put on ~15k miles before was bad, no difference.
- I have removed and cleaned the MAF, no difference.
- I have removed my stock air box to check for any leaks/replaced air filter, no difference.
- I have inspected just what I can see/feel/hear under the hood and notice no leaks.
- I have checked/cleaned the PCV related fail points and they are fine.
^ THIS ENDED UP BEING THE ISSUE -- READ POST 10 BELOW FOR SPECIFICS
- For the heck of it, took it under warranty to the dealer to have them inspect it, just in case they noticed something I didn't. They wouldn't even acknowledge the idle was rough...saying "its got 100k miles on it, it's normal."

My long term fuel trims are almost always at 0... +/-5...usually staying pretty accurately at 0 +/-2 under all circumstances, even after adjusting for WOT. But NOW, since this idle issue started I noticed as soon as I come to a stop my cars LTFT will creep straight up to 10-15 and stay there for as long as I stay in gear and stopped. This is 100% repeatable. Every other range of operation is normal except for idle. Car even still holds boost rather well for stock at 12.5 after settling.

A weird thing to note though, is that while stopped with my LTFT at +15, putting the gear in neutral or park will send LTFT right back to where they belong. So it "idles" perfectly besides when in gear and stopped.

Thanks in advance.
END ORIGINAL POST

 

[wpgsonic]

Although I have a 1.8 Sonic,I have basically the exact same problem you do.I have had the car in multiple times at different dealerships.They refuse to do anything,saying there is no codes or check engine light and that everything is nomal.Complete BS,I or anyone else would never buy a car like that if that was normal.It will idle so poorly it will almost stall at times.They even said they contacted GM engineering and they denied ever having any complaints about the issue or how to fix it...

 

[Italianjoe1]

I think it's the mounts. I notice it on my car with just under 50k miles, but i'm a tech so I'm more aware of it than most. It's getting to the point where my wife notices though, it's just excessive engine vibrations transmitted through the car. I want to replace all the mounts, they are a tad expensive though and right now the car is in the body shop. It may get done in the next couple months though, just to see what happens.

 

[Pirate Luke]

I haven't checked those, so I'm not saying you're wrong...but I don't think bad mounts would cause the change in fuel trims, at least in my case. The vibrations are just a byproduct of the surging.

 

[Pirate Luke]

We've gotta have a small vacuum leak somewhere. Everything I research/any experience I have point toward that. It's just a matter of finding it. In my instance with 100k+ miles, finding where it could be will take some time.

Still hoping anyone else that's experienced similar symptoms will chime in with what they've done.

 

[Maddmatts]

Two points of likely vacuum leaks on the 1.4T:
-The manifold pressure reference tube between the intake manifold and the turbo's bypass valve. The flexible hose connected to the intake can come loose, especially if you've done the bypass the bypass mod.

-Cam Cover pressure regulator failure. Pull the engine cover off and check the square vent hole on top of the regulator while the engine's idling. It should not be sucking air in.

 

[Maddmatts]

When my cam cover leaked it caused a rough idle and reduced brake effect. I can't remember if it gave a high idle out of gear or not. I did notice through my ultragauge that the commanded throttle % dropped to 3-4% when it's normally at 11-12% while stopped and in gear.

I just noticed you didn't mention a check engine light or any codes. Vacuum leaks almost always trigger a P0171 code for lean condition and sometimes a few others I can't remember off the top of my head.

 

[Pirate Luke]

Surprisingly no codes, though when my car was misfiring clear as day ~20k miles ago due to bad ignition coil it didn't throw a code either. I read some places say if at idle you have positive fuel trims and increase rpm to ~2500 and LTFT goes back down, its most likely a leak. When I do that it seems to match that expectation.

I'm hoping I find something when I give everything a good look over this weekend. In the meantime, ANOTHER issue....in disconnecting the battery for a moment, replugging is keeping the mileage at "---". Not sure why, but it's not keeping the car from working, a bit annoying though. There's a thread from others experiencing it here: http://www.sonicownersforum.com/forum/interior-ice-discussion/20100-anyone-know-why-my-odo-isnt-showing-up.html

 

[Pirate Luke]

Finally tracked the issue down to a worn PCV check valve in the intake manifold. It's got 104k miles now with no issue in the PCV system so far, so it's no doubt past the time many have issues with this little check valve.

Only reason it took so long to diagnose is because it's still there, and functions "MOST" of the time. Due to old age and oil residue it's time for replacement. Plan on implementing XtremeRevolutions fix from the cruze forum for longevity.

For what it's worth, anyone have any idle issues whatsoever with the 1.4L should check the PCV system first. It's this cars Achilles heel, for sure.

 

[Pirate Luke]

"Specifics Post"

I forgot to share these when I first started inspecting the PCV system a while back, but for anyone interested this is what a completely stock engines PCV system check valve in the intake manifold should look like compared to what it looks like after 100k miles before I cleaned it thoroughly. The oil residue had clogged the holes pretty well and the rubber was sticking in the inside if the manifold (where it was too hard to clean), preventing vacuum at idle from flowing properly from the crankcase.

Top view:

View looking directly at the check valve:

My check valve top view after 100k miles stock:

So I think it's safe to say, even if you don't do anything to this car, the PCV system should be something to maintain if you want engine longevity.
Here's the link to the thread explaining this system for any future readers: 2011-2016 Cruze 1.4L PCV System Explained

Anyway, I hope this thread helps others having similar issues.

 

[wpgsonic]

Has the design of the pcv system improved on the 2017 and 2018 models or is it the same?

 

[Pirate Luke]

Has the design of the pcv system improved on the 2017 and 2018 models or is it the same?

Based off what I've read here and a simple parts search indicate our 2nd gen sonics PCV systems remain the same, unfortunately. I know the cruzes and buick encores seem to have updated/different part numbers for their intake manifolds for the 2016+ models.

Can anyone who has a 2nd gen sonic or a cruze/encore mention if their PCV check valve is still an orange rubber piece inside the manifold or not?

 

[christian4917]

Yeah its the same on the 17'. 35k miles on mine and it looks only slightly better than the picture above and I'm already getting oil through the PCV hose into the turbo inlet. I'm on trifecta tune since around 5k miles so that didn't help. This thing needs a catch can for sure. Is oil in the turbo inlet going to cause any major issues? I will get a catch can on it, but I want to do the racerx intake manifold first to hopefully fix the issues I'm having with getting consistent power and to fix the check valve issues. Racerx also just came out with a fuel rail which I believe won't have to be modified like the stock rail does so might as well do that and get bigger injectors while I'm at it.

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[Pirate Luke]

Is oil in the turbo inlet going to cause any major issues?

It's hard to say for sure without seeing the rest of your PCV system. As long on your PCV systems check valves are still functioning properly I think installing an oil catch can would be fine. Many people with tunes here have done it. If you do it and find you're catching an excess amount of oil though, then you might have an underlying problem.

It's interesting to see how much more oil the tunes seem to push into that inlet. I ran stock tune for 100k miles and my turbo inlet has a fraction of what you have in yours. So being tuned, I think what you see is to be expected.

Are you burning any noticeable amount of oil?

 

[christian4917]

It's hard to say for sure without seeing the rest of your PCV system. As long on your PCV systems check valves are still functioning properly I think installing an oil catch can would be fine. Many people with tunes here have done it. If you do it and find you're catching an excess amount of oil though, then you might have an underlying problem.

It's interesting to see how much more oil the tunes seem to push into that inlet. I ran stock tune for 100k miles and my turbo inlet has a fraction of what you have in yours. So being tuned, I think what you see is to be expected.

Are you burning any noticeable amount of oil?

It hasn't been burning any noticable oil, but maybe I should check more frequently especially since its tuned. But this being my first turbo car I didn't know what kind of damage, if any, it would do to the turbo. Ill be upgrading that eventually but gotta get money straight first. So many mods, so little time [emoji23][emoji23][emoji23]

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