2018 Yukon Denali New Rough Idle

[Footankleg]

2018 Yukon Denali 6.2L, 95k miles. Recently started rough (previously smooth) idle while sitting at lights or in traffic. No codes. Tach does not move or jump, stays about 600 rpm. Mechanic changed plugs and wires, replaced an engine mount, did a fuel system cleaning with some machine and fuel additives (air idle control valve, cleaned throttle body, erc.). No change. Have run numerous tanks of gas, all premium, different stations. No change whatsoever.

Any thoughts what to try next?

 

[viven44]

You are posting in the 2021+ forum... but shaking at idle is generally due to an idle that is too low, or possibly a fuel trim that is either too rich or lean, our 2018 5.3 always had a 'normal' shake

If you have a timing light or a scanner, you can confirm what the actual RPM is.. the gauge being stuck at 600rpm is fine but it might be actually lower than that.

What does the fuel trim look like at idle ?

 

[Fless]

You are posting in the 2021+ forum...

Moved to the correct section.

 

[Joseph Garcia]

Do you have, or have access to, a quality bi-directional scanner? If not, I recommend that you get yourself a quality bi-directional scanner to add to your tool box. Then, you will be able to read ALL trouble codes, along with a brief explanation/pointer to the source of your issue. You will also be able to reset/delete trouble codes, after taking corrective action. You will literally save thousands of dollars in diagnostic and repair costs over the life of your truck, and you will most likely recoup the cost of the scanner within 1 year.

You will most likely need a tool like this to effectively isolate any issue that is affecting your rough idle.