Hi guys, I've been having issues lately with my 08 cobalt ss. I've been noticing the STFT at idle will at times want to peg at -30% and stay there for no reason. MAF was dialed in beginning of the year, nothing has changed. I re dialed it in again, and everything is good except for this weird idle rich trim.
Engine mods:
EFR6758
K&N short ram
ZZP IC
ZZP UCP
Catless DP
AEM alky injection
One step colder plugs
What I've done so far:
Boost leak test
Vac leak test
Cleaned MAF
Checked plugs
Retuned MAF curve and base multiplier table
Disabled the EVAP system isolating that from the engine
Had a clogged alky injector, cleaned that out, didn't even know it was clogged
Today with the attached log, i was going to do another MAF base multiplier table edit, after the second small pull, you can see the AFR drop like a brick all the sudden. Then at the end i pull into work and just sit at idle, again drops like a brick and stays there at -30% STFT. I can't find anything in the tune, but could use another set of experienced eyes to look it over incase i miss anything.
I'm at a loss here to what to try next to fix this issue. I'm going to try disconnecting the alky injector today, maybe that check valve is sticking open, or maybe its an actual fuel injector sticking. I need ideas please. Thanks everyone.