[Bayles76]

The following few paragraphs are going to be a quick history of what I've been dealing with. If you want to skip this part then I will have a marker for what I am currently dealing with and below that will be a quick summary of everything that won't be as long winded.


-History-

My 2016 2ss for the last 8 or 9 months now has been idling rough on cold starts especially in the mornings. It feels and sounds like it has a big cam in it for about 10-15 seconds then it calms back down and runs smooth as always.

Every since I first experienced it I have been trying to get to the bottom of the issue. It seemed to get worse when the temps here in Illinois were in the -20 area. (If there is snow or chance of snow I drive my jeep, just so a select few guys don't yell at me for driving my car in the winter).

So occasionally I will get a flashing check engine light for about 20-30 seconds after start up after it idles (more like chops/misfires) but every time I took it in to my dealership they have told me there isn't a light that comes on and seems to be a normal cold start.

Especially in the winter I would occasionally get a solid check engine light and the guys are Oriely's read it for me. It read "P050D - Rough Idle on Cold Start". Below that it has a not that says "No action needed".

So I took it back in to my dealership with the print outs from Oriely's and got the same sort of deal. "Well there is no code on here and we can't really do much if there is no code on while it's with us."

Starting to get upset at this point I picked up the car and brought it home. I have been driving the car as normal for the last couple months now and it seems as it's getting warmer the code doesn't come on anymore other than the random flashing check engine then that goes away. The car runs like a top as soon as it starts warming up as it should.


-Current Situation-

I took my car into a new Chevy dealership for it's service yesterday morning. I have been starting to get frustrated with the original dealership I bought the car from.

I told them its just in for a oil change, multi-point inspection, and it has an appointment with the detail bay to get its spring cleaning done. I also told them about the rough idle first thing every morning when you start the car. They said they will check it out and see what's going on.

Last night I received a call from the service manager. He said "So we felt the rough idle cold start like you mentioned and something defiantly isn't right". "We are going to leave it here again over night check it out again in the morning to see if we can identify the root of the problem".

At this point I am thrilled someone it taking it seriously. I wan't ready for how serious this issue could be though. "I have only seen one other case of this in the last couple years and it was with another 2016 camaro ss". He then followed with "This is worst case scenario but I want to check and make sure that you aren't getting antifreeze in your cylinder over night". He said that "What could be happening is that over night some antifreeze is leaking into the cylinder then in the morning when you start the car it misses in that cylinder because it has antifreeze in it and takes 20 seconds or so to get it out and then the idle returns back to normal".

My heart sank and I realize this could be a much bigger issue than what I previously thought. This morning they are going to put a oscilloscope down the spark plug hole of that cylinder and see if that is indeed the issue. He said it could also be a bad injector or even something wrong with the ECU.


-Summary-

I have been dealing with a rough cold start idle since the fall and It seems to have gotten worse over winter in the freezing temperatures. After about 20 seconds it goes back to a normal smooth idle and runs like a top especially once it starts to warm up. I took it to my dealership and they told me that it seems like nothing is wrong. I took it to Oriely's to have the check engine light that comes on occasionally and they said it is "P050D - Rough idle on cold start" with a list of issues and fixes to correct it. My dealer again told me that if there is no Check Engine Light on when they have it they can't do much.

I took it to a new dealership yesterday Tuesday night for a service, spring inspection, and detail appointment. I told them to check out why it idles so rough in the morning. They called me back yesterday and said there is defiantly something wrong. They think it could be as serious as leaking antifreeze into the cylinder over night which is causing the missing every morning. They will be putting and oscilloscope down the spark plug hole this morning to see if our worst fears are real or not.


-Conclusion-

I am now anxiously waiting my call from the service manager to give me the verdict and what they are going to do to fix it. I will update this thread as soon as I have any news from the dealership. Please feel free to share you opinions and past experiences if any of you have had this same issue.

Thanks all, happy Thursday!

[EMTNLSS]

Yep I have this exact same issue. Codes P050D and P0300. I've logged it with hptuners and it's misfiring in cylinder 7 and 8 for me only during the cold start sequence. Like you said as soon as the rpms drop to around 700 I get no misfires. I can drive it around and hptuners shows no misfires. I bought some new injectors and will be replacing them as I believe that's the issue. During a cold start the injectors run in a special mode that pulses them twice or something like that and in hptuners I can watch them switch off that mode. As soon as that happens the misfires stop. So i'm hoping once I get the injectors replaced it'll be fixed. If not then maybe ported heads are in my future. Definitely looking forward to your update.

Also here's a link to that coolant leak service bulletin the dealer was talking about if you want to read into it more: https://gm.oemdtc.com/9941/ses-lamp-...-chevrolet-gmc

[Bayles76]

Originally Posted by EMTNLSS

Yep I have this exact same issue. Codes P050D and P0300. I've logged it with hptuners and it's misfiring in cylinder 7 and 8 for me only during the cold start sequence. Like you said as soon as the rpms drop to around 700 I get no misfires. I can drive it around and hptuners shows no misfires. I bought some new injectors and will be replacing them as I believe that's the issue. During a cold start the injectors run in a special mode that pulses them twice or something like that and in hptuners I can watch them switch off that mode. As soon as that happens the misfires stop. So i'm hoping once I get the injectors replaced it'll be fixed. If not then maybe ported heads are in my future. Definitely looking forward to your update.

Also here's a link to that coolant leak service bulletin the dealer was talking about if you want to read into it more: https://gm.oemdtc.com/9941/ses-lamp-...-chevrolet-gmc

Funny you mention that TSB. That's exactly the procedure that they took!

Yesterday the service manager called me with an update.

Thankfully nothing was found in the cylinders that were missing yesterday morning. After they checked them out and determined that wasn't the cause they then took to the TSB and found that the injectors were faulty.

It is still waiting at the dealership for its new injectors then hopefully i'll be able to pick the car back up tonight.

I will update this thread when I have more information.

[Bayles76]

Just to update my original thread,

I picked up my car last night. She is running silky smooth now even when cold. Let it warm up completely before rolling into the throttle a few times to make sure all was working as it should. Very happy with my dearlships investigation, diagnosis, and action.

I would've had the car Monday morning but I was busy and wasn't able to pick up the car until last night.

Couldn't be happier!

[EMTNLSS]

Awesome! I'm excited to get my injectors replaced then and have it back to running like it should.

[SSDan]

Originally Posted by Bayles76

Just to update my original thread,

I picked up my car last night. She is running silky smooth now even when cold. Let it warm up completely before rolling into the throttle a few times to make sure all was working as it should. Very happy with my dearlships investigation, diagnosis, and action.

I would've had the car Monday morning but I was busy and wasn't able to pick up the car until last night.

Couldn't be happier!

Great news! So glad you got it back and its running properly and that the existing TSB took care of the issue.

[sav03cobra]

Originally Posted by Bayles76

Just to update my original thread,

I picked up my car last night. She is running silky smooth now even when cold. Let it warm up completely before rolling into the throttle a few times to make sure all was working as it should. Very happy with my dearlships investigation, diagnosis, and action.

I would've had the car Monday morning but I was busy and wasn't able to pick up the car until last night.

Couldn't be happier!

Was yours bucking/high idle on Cold Starts? Then running fine after about a minute of warm up?

[TJay74]

Yep, that is the sign of a bad injector. Had the same issue on my 2016 GMC Sierra and ended up with a new injector.

[sav03cobra]

Originally Posted by TJay74

Yep, that is the sign of a bad injector. Had the same issue on my 2016 GMC Sierra and ended up with a new injector.

Is there a way to log which injector it could be? Via SCT software?



No CEL/codes on my dash.

[EMTNLSS]

Originally Posted by sav03cobra

Is there a way to log which injector it could be? Via SCT software?



No CEL/codes on my dash.

I don't know about SCT but with HPTuners you can log which cylinder is misfiring which would show it's that injector. I would imagine there would be something similar with SCT if you had there tuning software.

[AdmAnt13]

Originally Posted by sav03cobra

Was yours bucking/high idle on Cold Starts? Then running fine after about a minute of warm up?

Originally Posted by TJay74

Yep, that is the sign of a bad injector. Had the same issue on my 2016 GMC Sierra and ended up with a new injector.

Mine does this every time but was told on another thread this is completely normal.

[LT4Greg]

My 2016 SS had the same code show up and the tech at the Chevy dealership found 2 injectors were bad and replaced them under warranty and the car ran like it did when it was new. Of course I don’t have it now because I bought a low mileage used 2017 ZL1 back in March.

[EMTNLSS]

So I replaced my injectors today and it sounds and feels so much better now. Before it sounded and felt rough during cold start. Before I would log it with HPTuners and get 100's of misfires in cylinders 7 and 8. Logged it after I replaced them and got 0. I forgot that it was supposed to sound like this because of how long it had been happening lol.

[AdmAnt13]

So when it’s colder in ambient temp, and the car is cold starting, if I rev it will hang.
This never happens once it’s warmed up.
On top of that if I don’t let it warm up and start driving, the car kind of bucks.

Have no codes. Just had it scanned two days ago. Think I have the same issue?