Hi guys

Brand new 2015 suburban. Truck idles rough. Stays at 500 rpm but every few seconds drops down a bit then goes normal. Not super bad but definitely doesn't feel right. It has been to dealership 4 times for this and they say its normal. Overtime they keep the truck they give us a new loaner tahoe (which supposedly has same engine) and it doesn't do what my suburban does. I believe they have changed motor mounts already but it didn't do anything.

They are telling me this engine purposely misfires a cylinder to do a diagnostic check. They are saying it does this every few seconds when at idle.

Does the engine actually do this? I googled but can not find anywhere where it says it purposely misfired every few seconds for diagnostics.

Any help or suggestions would be great. I would just like to have a normal idle like the tahoe has. I tried another new suburban at dealership and it idled fine. Dealer didn't have an answer to why that one was smooth and mine is not. i asked shouldn't that one also misfire a cylinder for Diagnostics

Thanks for everything, you guys are the best

Peter

 

You might consider purchasing gas from a different station.. its possible the gas you are using is the problem.

 

don't happen to have the a/c or defrost on when you notice this do you?

 

I have a 2013 which I bought a year ago and noticed a slight roughness in the idle. After some research I found it to be common because of how lean the car runs at idle to save fuel. I ignored it but one day the roughness turned to a blown misfire at idle although it drove ok. Check engine light came on with misfire in cylinder 7. Traction control light came on as well as that system malfunctions when there's a misfire. Brought to dealer very concerned about a afm problem. Turned out to be a broken valve spring on cylinder 7. Dealer fixed under 100k powertrain warranty. Idle roughness improved after the repair although I still feel it very slightly once in a while.

 

I have the same issue with my 2015 Tahoe. They say its normal, yet I've driven a number of rentals that have no issues.

I've taken it to 2 different dealers and both gave me a line of BS why it happened, yet they cannot do anything about it.

I am not a technician, but here is what I found out.

The problems seems to be that this engine is not working properly when it idles near 500 RPM or below. It starts stalling, and then the computer realizes it and starts compensating which brings the RPM back up creating the very uneven pattern.

SIMPLE FIX would be to increase the RPM by 50-75 where it stops idling rough (simply try using your foot and softly add a little gas - you will notice this problem stops immediately).

I used friend of mine's tuner and increased the RPM by a little bit - and oh happy day it worked. No rough idle once the engine runs above 525 RPM.

The problem with this fix is that it could void your warranty. So do not do it. Nonetheless it worked.

It seems all Chevy would have to to is to increase the idling RPM while driving by a little bit to fix this issue. Yet no one seems to care.

There a lot of people out there who are having this issue. Chevy will not going to come up with the fix unless we organize and make noise. A $50K-$60K vehicle should not have this type of issue.

I contacted a lemon lawyer in my state asking what can I do about this situation. Will let you know what happens.

 

500 rpm seems like a low idle speed for sure.
would a throttle body clean help?
any issues with a cold start and stall?

 

Yes. The throttle body was cleaned by dealer, emission as well as fuel injection serviced. All the things the dealer was able to come up with I did.

There are hundreds of similar cases. I did some research online. Mostly V8 engines.

To me it seems as Chevy is ignoring this problem that's why I contacted a lawyer.

The technician at dealer told me today that he sees there is a roughness, but cannot do anything to help me any further. So I should just accept that my $50k vehicle is acting like a junk car.

I'm ready to bring in media, lawyers and lemon law.

 

My 07 Tahoe with the 5.3 motor that I once owned exhibited this so called "problem" you describe. My current '13 Tahoe with the same motor also exhibits this "problem." My best friend has a '11 Burb, like my Tahoe, has the same 5.3 motor and has this so called "problem." Even my '08 Merc E350 has a slightly fluctuating idle!!! Despite this perceived "problem," all of these vehicles run perfectly fine. There's no problem, drive on.

Lemon law??? Lawyers??? Geezzzzz........

 

how do you think that will work out for you?

 

I find the rough idle is usually gas issues. When it happen sot me I use a can of techron and super unleaded. That cures it almost all the time;