Rough idle

[Bo Patrick]

Rough idle 2015 Chevy Silverado 6.2 litter idle rough when warm in ND out of gear

[1SLOW1500]

hhhhmmmmm...

remove intake and tb. wipe with clean paper towel then spray and wipe down, set aside and let dry. pull the maf and use maf cleaner to spray that. reinstall and re calibrate tb. 

If it is a misfire we have different instructions. 

all this is assuming you don't have a code reader or better a scanner? 

[Baytrucker]

Mine does this as well. The way GM tunes their engine is that when its warm (above a certain temp), the idle drops as low as 450RPM. I noticed that when my needle went below 500, there was a noticeable surge every few seconds.

 

I took it into GM, and they said this was normal. I think they are full of crap. Cleaning out my TB helped a lot.

 

To clarify what 1SLOW1500 said above, you should try cleaning your "tb" (throttle body), and maf ("mass airflow sensor").

 

The throttle body is a damper that opens and closes in response to pressing the gas pedal. It tends to get filled up with carbon over time. Carbon deposits get sticky when hot. This can cause your damper to stick a little, especially towards the closed position when its warm. If your damper is sticking, this can cause your engine to surge, especially when warm. GM tunes these engine to run at the bare minimum RPM to meet their EPA requirements, so your throttle needs to be clean and operating like a swiss watch for your engine to run smoothly.

 

Here is a video:

Throttle Body Clean

 

Word of warning. If you pull the thottle body, do not adjust the damper by hand while cleaning unless you have the means of calibrating it afterwords (a ODB utility tool will do). Otherwise, leave it in the position it is in when you pull it. The video mentions this. The consequence of not following this advice will mean your truck will start idling at ~2500RPM until the computer clues in and runs the diagnostic. It can be a little scary, but it shouldn't hurt anything.

 

As for the mass airflow sensor, this pretty much works as described. It detects airflow through your intake. This reading is used for a bunch of things, and when its clogged with carbon and other gunk, it doesn't read properly. On these trucks, its usually positioned right near the filter box on the passenger side. I'm at work now and can't find the link to a good video, but I'll try to post one later. Cleaning the MAF is stupid easy. You just have to remember that the MAF sensor is delicate, so be gentle with it.

 

If your truck isn't throwing a code, it is very likely that a idle surge when warm is one of these two things. Most honest mechanics will clean your TB and MAF for you for the cost of an hours labor, if you aren't comfortable doing it yourself. Its a really good starting point to solve your idle problem.

 

Good luck.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Edited July 8, 2019 by Baytrucker

[Bo Patrick]

4 hours ago, 1SLOW1500 said:

hhhhmmmmm...

remove intake and tb. wipe with clean paper towel then spray and wipe down, set aside and let dry. pull the maf and use maf cleaner to spray that. reinstall and re calibrate tb. 

If it is a misfire we have different instructions. 

all this is assuming you don't have a code reader or better a scanner? 

It's not throwing a code just have a rough idle I know it's the 6.2 and it's not smooth like the 5.3 or 5.7 vortec but it's not the cam it's a stumble rough cut out idle 

[1SLOW1500]

What is the engine temp and the idle rpm?
Just because there isnt a hard code doesn't mean afr or misfire isnt happening

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