ok so in everything I have been able to find, there doesn't seem to be a clear answer/solution to the Gen 3 lean hot startup issue. Most have said its IAT heat soak (which it can be for sure) but there seems to be more to it than that.
this is on a 1999 Trans Am with the stock ECU, cammed, turbo, 3 bar OS
here's what I did today to try to test this out:
- Cold start from siting overnight, it's 59* out today. drove around for quite a while gathering VE data...I'm running rich all around, sometimes as much as 20%. IAT's around 59*-62*
- idled stopped for maybe 10 minutes until it heat soaked the IAT and I was seeing 97* IAT temps and it started hitting 17-18 AFR
- shut it down for maybe 5 minutes. hard start (almost didn't actually) and IAT's are at 95*. hitting 17-20 AFR at this point
- drove it around with AFR locked around 11.4 to let it actually drive. within 10 minutes or so I was back down to 64* IAT, turned off AFR lock and seeing 16-17 AFR
- Drove it around some more until IAT went to 61*, AFR at 14-15. Better but still higher than it should be, even with IAT normal
- drove it around ~10 minutes more, no change...AFR still 14-15 and IAT still 59*-61*.
I attached logs of the normal drive and after the IAT had cooled down as well as my tune...
so something else is adding to the issue other than just IAT soak...there has to be some other factor...another sensor heat soaked, some part of the code or table we can't see, something.
I could flash to a 2002 OS but if IAT soak isn't the problem, changing the bias table won't really help right?
Has anyone made any headway in determining what else could be contributing to these issues we are experiencing?