So I've been swapping tunes in my 01 duramax and data logging the results. Mostly tcm tunes but I did try an ecm tune that I found here in the tune library, the No logic 3.0 lb7 tune. Tried it out but couldn't run it, made way too much noise. Sounds like a really cold diesel even though truck was warm. By the time I turned around and made it home I had developed an idle lope in park. Not bad but certainly noticable, goes away when in gear or I turn on the ac. I flashed the ecm with the stock file and it still does it ! Went for a good run, no change still lopes. Let the truck cool down a bit, flashed in my tune that I've been running for years. Still does it...WTF.. I went for a longer drive, now it idles without lope in park but lopes in gear and or when you turn on the ac ! .. Is it possible this could be related to my tcm tune somehow? What tables are commonly used to affect idle stability ? And since I returned it to stock and still had the issue what hard parts could be upset about my tuning adventures?
New Development, unwanted idle lope ...
- Thread starter gearguts
- Start date
Since it does it with whatever tune you put in, its not in the tuning. Its either the FPR on the CP3 has gone bad or inlet fuel pressure to CP3 is too high. I have run the NoLogic3 tune for a while now.....absolutely no issues whatsoever. Dave did a nice job on that one. 
.....and for God's sake, stop messing with the TCM tuning before you actually hurt the transmission.
.....and for God's sake, stop messing with the TCM tuning before you actually hurt the transmission.
Datalogged it today. I cant see anything wrong with fuel pressure. It seems to be related to MBPW and MFUEL mm3, both show a saw tooth pattern that is pretty well synchronized from what I can tell. I hope I havn't hurt my computer or fuel module. I'll attach the log, i'm sure there's more there than what I know to look for.