After the engine has had a good highway run, if I park and go back out in say 30-45 mins, the AFR's go crazy high (~18-19). So high that it is pretty much un-driveable in stop-go traffic (stick shift). I think heat soak is the culprit, and have tried to decrease the IAT correction factor, increase after-start enrichment values, etc.
However, if I give it a WOT run, the AFR's are normal. So the problem only happens in the low MAP bins. This has led me to believe the problem lies elsewhere. Particularly in the injector open/close time. Correct me if Im wrong, but everything else in the injector pulse time calculation is linear. It makes no sense that AFR's go high ONLY at low MAP values (~ <50 kpa). Again, they remain lean for a while until I drive the car on the highway for like 3-4 mins. It will NOT correct itself during stop/go traffic. In fact, the issue also shows up if driven in stop/go only.
To test my idea, I've changed from 1 simultaneous injection pulse to 5 simultaneous (only 'other' option available: engine is a turbo 5 cyl, VR on crank, hall on cam). When the setting is changed to 5 simultaneous, I try to adjust the injector dead time to get the same AFR's while idling. AFR's go lean when changed to 5 simultaneous. However I cannot get the AFR's back to where they were. I must change the VE map for it to just idle!
Haven't tried driving with 5 sim, since Im pretty sure it will result in not enough injection time / reaching 100% duty cycle.
So Im stuck with lean AFR's when hot. Injector dead time is set at 0.8ms right now. Injectors are bosch: http://www.witchhunter.com/flowdatapix/b0280155766.jpg
Any ideas how to fix this problem?
Am I on the right track here? Any other suggestions what to try?