Idle adjustment 5.3

bulldog77 · November 8, 2019

I have a 2016 Sierra with a 5.3 and when it is idling in gear it is a little rough. I can put it in neutral and it smoothes out. I showed my dealer what it is doing and asked him to turn the idle rpm up and he told me that they can't adjust the idle that the computer does it. I have never seen a truck that you couldn't adjust the idle on. My question is have any of you folks figured out how to adjust the idle on one of these engines. I am having quite a learning curve here coming from years of owning diesel pickups. Thanks for your help.

HeySkippyDog · November 8, 2019

It's true, you can't adjust the idle unless you reprogram the parameters in the computer. But why would you? If it's idling rough, it has a problem that needs to be fixed.

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paumat · November 9, 2019

13 hours ago, bulldog77 said:

I have a 2016 Sierra with a 5.3 and when it is idling in gear it is a little rough. I can put it in neutral and it smoothes out. I showed my dealer what it is doing and asked him to turn the idle rpm up and he told me that they can't adjust the idle that the computer does it. I have never seen a truck that you couldn't adjust the idle on. My question is have any of you folks figured out how to adjust the idle on one of these engines. I am having quite a learning curve here coming from years of owning diesel pickups. Thanks for your help.

It’s a known issue and the claimed fix is updated motor mounts. Helped mine considerably but didn’t completely eliminate it...was covered under power train warranty.

mookdoc6 · November 9, 2019

15 hours ago, bulldog77 said:

I have a 2016 Sierra with a 5.3 and when it is idling in gear it is a little rough. I can put it in neutral and it smoothes out. I showed my dealer what it is doing and asked him to turn the idle rpm up and he told me that they can't adjust the idle that the computer does it. I have never seen a truck that you couldn't adjust the idle on. My question is have any of you folks figured out how to adjust the idle on one of these engines. I am having quite a learning curve here coming from years of owning diesel pickups. Thanks for your help.

Why you getting away from the diesels?

Anyway, 1st you can't adjust idle parameters unless getting into ECU and reprogram etc. "TUNE" GM will not allow it to be done at Dealership. Their a couple TSB's like Motor mounts, updated parameters for janky idle etc.

Problem is once HOT GM has it drop to 500rpm's in the name of economy. Coupled with a semi aggressive Factory CAM it's inherently rough when HOT/IDLE in DRIVE.

Have a seasoned tuner bump up the mapping for hot idle 75rpms, 100rpms it will help immensely. Yes, it will consume slightly more fuel? Who cares you will still not get silky/smooth because of the CAM profile....oh,well it's a truck?

bulldog77 · November 9, 2019

Mookdoc6,

We have quit camping and I just don't need trucks as big now plus the maintenance is high but I will say this GMC sure does ride a whole lot better than a Ford F-350. Thank you for your input.

flyingfool · November 10, 2019

idle is usually controlled by your timing on modern engines, do a live data scan record and monitor what you find. check for any error codes, maybe your using cheap gas and its messing up idle?