2015 Tahoe/Rough idle

[Twood2006]

Have a rough idle only at a dead stop other than that runs fine. But it is throwing an engine light, took it to dealership had it scanned and this is what it showed any ideas what it could be. I have replaced the MAF sensor new plugs and throttle body new. But it does not always have a rough idle, sometimes it runs perfect it just randomly starts having a rough idle. It may go three to four days with no rough idle then it may start and stay rough for a couple of days. Also this morning for the first time when I was slowing down as it was down shifting it was not smooth, but rather like it was kind of slamming into the next gear but not real hard.

 

[Joseph Garcia]

I cannot personally help you with your question; however, other members on this Forum that are much more knowledgeable than me will chime in.

 

[B-train]

Is your truck stock? Do you use anything to turn of AFM? What is your usual oil change interval? Do you get gas at the same place?

Can you drive in manual for a few days and lock it in 5 (6 speed) or 7 (8 speed). Just suggesting something to keep the AFM lifters from actuating for a couple drive cycles and go from there.

As far as fuel goes, that's a big IF. But, perhaps you got some water or crappy fuel on your travels. Not sure how often you fill up, but maybe running some ATF in the next tank could be a test (1/4 qt per full tank should work. High detergents and lubrication)

 

[THarber]

Did you buy AcDelco or knock off MAF and TB? It does make a difference. Also how about the MAP?

 

[Twood2006]

Yes my truck is stock, also I get gas at the same place every time unless I am traveling. The AFM is still on I have not done anything to turn it off. Now I will say, I took your advice and have been riding with it in manual (5th). After driving it like that for 3 days, I was on my way home last night and was in a drive through line. I noticed that it was idling so smoothly almost couldn’t Feel it, looked down and the check engine light had went off. Then I woke up this morning and left to go to work and the light is still off and it is still idling and running perfect no problems. I wonder what it could have been, and if it will stay running perfect with no rough idle? Anyways thanks for the suggestion fingers crossed it stays like it is.

 

[B-train]

Well, that's a win! I'm speculating carbon buildup or some lifters that were sticky. I'd recommend running a half quart of ATF in the oil for the last 200 miles or so before your next oil change. That will help remove carbon buildup and wash the motor.

I did that on my 2017 with the 6.2L last oil change. Probably ran it 100 miles or so and the oil came out dark. I have AFM off and change at 5k-ish. I know that the direct injected motors can have more carbon buildup due to the valves not getting washed by fuel.

Mine is due to for an oil change soon and I plan on doing that again. If you feel unsure, you could do a short change interval with new oil. Run it for a bit and note the color. Then add ATF, drive it, and see how it looks. The ATF will change the color a bit, but it will probably get darker pretty quick.

 

[B-train]

The reason I did it initially was because I heard a lifter tick one day at startup after it had already run that day. No noise since. Stupid emissions regulations......