Quote:
Originally Posted by adynes
Jason, is there a throttle Accel enrichment variable that is specific to the warm-up period? From what I remember seeing in the datalog, the lean spike at tip-in is worse at the start of the log when coolant temp is low, the gets better as the engine warms.
Edit: I just re-read your first post where you mentioned the three temperature setpoints
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Yup, the dTPS gain is always functioning since it's based completely off the TPS signal.
The Accel and Fast Accel tables have three breakpoints. 20, 65 and 170 degrees and will interpolate between those break points. You can change these breakpoints in the ProCal software. I actually need to do this on mine, fueling at around 140-150 degrees temp on my issue is problematic. Since my car is always garaged and never sees temps below about 40 when cold, I can modify that a bit.
What's really happening here is the added fueling to keep the intake runners wet. The pontiac engines have very large intakes with a lot of surface area, which is one of the reasons this issue crops up eventually, the base table just doesn't understand how much fuel film there is on these engines. It takes some hints from the provided CID, but that's it.
So what you're seeing in the graph is initially, all is well, but shortly after tip-in the runners dry up as not enough fuel is being provided, the engine goes lean then the trim freaks out, over corrects and causes a decaying oscillation between lean and rich until it finds itself.
That's a symptom of the "self learning" as there's simply too much adjustability between the trim and learn value (in some cases about 50-60% correction). Typically one the system has had a good amount of miles and varying conditions on it, it's good to turn off the learn and in some cases if your learn and trim values are very close to 0, also limit the trim amount.
I do think the OP does have something ignition related going on here, but this lean tip-in issue is also playing a part in his issue.