Uneven Idle is getting progressively worse but cannot find the cause (Fuel Pump / Injectors?)

[SNES Avalanche]

Removed / cleaned / tested all 8 fuel injectors / replaced the O Rings and there's 0 change.

I'm at a loss for what else it can be but the idle is terrible.

 

[donjetman]

Coil?
Also do a compression or leak down test.
Tools are inexpensive from harbor freight

 

[bdbull]

Does this engine have AFM? If so, I'm gonna go out on a limb here and say it has something to do with the AFM. I pretty much had the same symptoms as you, and now I'm working on fixing a stuck lifter. Slightly rough idle for quite a while now and just last Monday threw all kinds of lights on the dash and a misfire on cylinder 6 code. Got the tool from CrazedPerformanceRepair to fix the lifter today so will be working on that soon. Also, just sent my computer off to lt1swap.com to delete the AFM. If your engine has AFM, I'm willing to bet it has something to do with that.

 

[SNES Avalanche]

Does this engine have AFM? If so, I'm gonna go out on a limb here and say it has something to do with the AFM. I pretty much had the same symptoms as you, and now I'm working on fixing a stuck lifter. Slightly rough idle for quite a while now and just last Monday threw all kinds of lights on the dash and a misfire on cylinder 6 code. Got the tool from CrazedPerformanceRepair to fix the lifter today so will be working on that soon. Also, just sent my computer off to lt1swap.com to delete the AFM. If your engine has AFM, I'm willing to bet it has something to do with that.

Checked both sides of lifters and they’re all moving correctly / the engine has 35k miles as the first one died of lifter failure.

 

[bdbull]

Checked both sides of lifters and they’re all moving correctly / the engine has 35k miles as the first one died of lifter failure.

Yeah, I'm not necessarily suggesting you have stuck lifters. Just that the AFM has something to do with your problem. I had a rough idle but no stuck lifters either...until I had a stuck lifter. My engine is a little different though with 213k miles on it. I've done a ton of reading and watching youtube on AFM lately (obviously) and I'm convinced it is from the devil. Check out the CrazedPerformanceReview youtube channel and you'll want to rip that AFM crap out immediately. Lots of good information there on a terrible design from GM.

 

[Mickey_7106]

What obd2 reader did you
use with Torque pro. I want to get Thor set up for my 2011 6.2 yukon

Obdlink mx+

 

[SNES Avalanche]

Quick update.

Replaced Oil Pickup Tube O-Ring / replaced the leaking Oil Cooler block and that helped oil pressure a hair, but the idle issue is still there.

I know the Passenger Side Motor Mount is bad so I'm going to tackle that next but I'm at an absolute loss at this point.

 

[Fless]

FWIW I'd be looking at the Idle Air Control part, maybe think about a different throttle body as a test.

Has a comparison been documented of the pedal position sensor vs the throttle body position? Maybe graph both to see if they're tracking?

 

[SNES Avalanche]

Well it wasn’t the pickup tube O ring or the passenger motor mount.

This might be the most frustrating mystery of all time.

 

[FasterBass]

Any update here? I also just went to iridium plugs, and I have read a few posts about poor idle after putting them in. I'm swapping in basic copper plugs this weekend to see if that does anything. AFM is deleted, Put the shield on the oil pressure release valve and also have a valve cover and catch can going on this weekend.