Idle Issue... still. PCM/Tune issue?

[jack0255]

I had the same kind of issue with my 04. Check to make sure the throttle body is not sticking. You can check by turning the key on and have someone step on foot peddle and watch the butterfly and make sure it is not hanging up.

[farmtruc]

if your scanner will show left and right trims, lmk what those report.
we are looking for a correction of either lean or rich.

see what the ltrims are at idle, cruising and semi aggressive.

you can email me the results if the scanner will export a file.

[pl4yboy]

The z06 MAF could be throwing off the idle airflow table? Maybe?

[rkwhite61]

if your scanner will show left and right trims, lmk what those report.
we are looking for a correction of either lean or rich.

see what the ltrims are at idle, cruising and semi aggressive.

you can email me the results if the scanner will export a file.

Thanks! I see some type of trim data in the log (I'm green when it comes to this stuff). Didn't get your email so I mailed the file to Erica. Data is from idle to mild cruising, back to idle then mild cruising again (basically repetitive stopping and starting where I'm seeing the issue). Hope it helps.

[rkwhite61]

Swapped MAF's with the Suburban as a test. No difference, still has same symptoms as initially posted. One other thing I noticed - the rpm, after the abrupt drop, is never below 716 in the logs.

[farmtruc]

If I have the correct customer an file Ronnie?
Then the idle is at 625rpms, so something is keeping the idle up, vac leak, mechanical issue, etc.

lmk if that's you.

[rkwhite61]

If I have the correct customer an file Ronnie?
Then the idle is at 625rpms, so something is keeping the idle up, vac leak, mechanical issue, etc.

lmk if that's you.

Yep, that's me. I've checked and rechecked for vacuum leaks (even replaced intake gaskets very early on) and most recently, even bypassed the brake booster. As for mechanical issues, not sure what it would be. TB seems to closing all the way. Guess I could buy a new IAC, but was hoping not having to throw dollars at new parts if I'm just guessing at this point. The abrupt change in rpms from 1100 - 700 after stopped for 2-3 seconds is puzzling - why I asked about a possible PCM/Tune issue. Any luck with the logs I sent your way?

[farmtruc]

The scans aren't really real time, just text with freeze frame data.
But after looking thru them, the maf is fine!
The ltrims are hovering around slightly negative, so that's good.
If it was the maf, the ltrims would be extreme one way or the other, not in this case.

Have you ever checked vacuum leaks with a smoke machine?

[rkwhite61]

Great, thanks.. good to know on the ltrims.

Haven't checked with a smoke machine. Can you bring me yours? lol j/k. I'll see if I can rent one around here. If not, I saw a few videos on how to build one. It may be a few days or early next week before I can get around to doing it. Wife's got me doing some honey-do's over the next few days. Stay tuned. Again, thanks for your help so far... much appreciated.

[rkwhite61]

Just completed the smoke test. No leaks anywhere (other than around my shitty tape job trying to block-off the front of the TB). Thoughts? What now?