2018 Yukon Denali/Rough Idle

[qfastvette]

I have a 2018 GMC Yukon Denali 6.2
I have been having problems with rough idle in gear when stopped. I have read some post about the rough idle being motor mounts etc. I have replaced mine because they went bad at 50k miles. I have been dealing with this from the day I bought the truck brand new in 2018.
I will say its gotten worse over the years/miles driven. I also noticed if I don't run 93 octane fuel and run 87, 89 or 91 it gets much much worse as the octane is lower. I know it recommends 93 octane but some times a gas station might be out so I put a lower octane and thats when it much worse. When I take it to the dealer they say that their is nothing they can do with no check engine light. But the dealer will also tell me this is normal. I even tried to trade it in and they said what is wrong with the truck and didn't went it on a trade in. Please tell me someone has had same problem and got it fixed.

 

[swathdiver]

I have a 2018 GMC Yukon Denali 6.2
I have been having problems with rough idle in gear when stopped. I have read some post about the rough idle being motor mounts etc. I have replaced mine because they went bad at 50k miles. I have been dealing with this from the day I bought the truck brand new in 2018.
I will say its gotten worse over the years/miles driven. I also noticed if I don't run 93 octane fuel and run 87, 89 or 91 it gets much much worse as the octane is lower. I know it recommends 93 octane but some times a gas station might be out so I put a lower octane and thats when it much worse. When I take it to the dealer they say that their is nothing they can do with no check engine light. But the dealer will also tell me this is normal. I even tried to trade it in and they said what is wrong with the truck and didn't went it on a trade in. Please tell me someone has had same problem and got it fixed.

What kind of gas mileage are you getting?

Have you replaced the plugs and wires? If not, you ought to, regardless of the mileage. At the very least, pull the plugs and inspect them. If you don't know know what to look for, take pictures and post them here and the fellas will examine them for you.

Where do you live that runs out of 93?

 

[Bob2C]

I have an 18 Tahoe with a crappy idle since day one. The dealership changed the motor mounts which helped a bit but still felt the stumble while in drive stopped. I got fed up and raised the idle to 600 RPM all the way around. Smooth. Then I decided to tune it to 93 which was my original intention. Mine would idle at under 500. Around 475 which I think is too low. I have read other have complained about using 87 octane and it’s terrible. I did not have that problem after I raised the idle and before the tune. I find by me bjs gas to be the best. Costco. Meh.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage feedback from the knowledgeable folks on this Forum.

My 6.2 has a very minor rough idle, in that is not glass smooth, but there are no issues otherwise with the motor. I also have a 93 octane tune, but it idled no differently before the tune, when I ran 91 octane.

If your dealership is telling you that they cannot do anything without the truck throwing a DTC code, that is BS, I analyze my truck's systems all the time with my Tech 2, without first having to receive a DTC code. If there is another dealership in your general area (I know, in many places, there are no 2nd dealership options), I would suggest going to them instead. The best alternate potential solution is to find a local knowledgeable auto repair shop, if one exists.

Other folks on this Forum will chime in with their thoughts.