Help!! Starting/idle issues after turning off (logs included)

[paulglasper]

hi guys i have posted this a few times but not had logs to show you guys

so basically my car in an ultra4 car in the uk. and since i have had the engine it has had a weird starting issue when its turned off for a few minutes. never been able to work out the cause.

anyway i managed to get it to do it the other day whilst logging and as you can see the first log car is idling with about 7g/sec off idle air and 30-40 IAC counts

turned off for around 2 minutes and that is the 2nd log, sruggled to start and then when it eventually did it required 18g/sec of idle air around 185 IAC counts

this really screws me at races as i cant predict when it will do it and it means that the cars dies when coming back to idle when letting off the throttle

i have replaced the throttle body with a new fast 102, new genuine IAC and new TPS last week and the problem is still exactly the same.

If anyone has any ideas or has seen this issue before i would be extremely grateful

i cant understand why with the same spark (22deg), same air fuel (around 14.5) the car suddenly needs twice as much idle air

many thanks

Paul

[smokeshow]

The first file contains no start info. Need information on injector pulse width, intake valve temp, MAF signal. And before you do anything, divide your cranking spark in half... And post the actual file.

[paulglasper]

Thanks for reply.
I will try get new logs tomorrow with extra info.
The main thing I was wondering about is the Engine not requiring the same airflow at idle. Surely that should never need to change if temp etc are constant. Just really confuses me

Car is speed density so no MAF

Cranking spark is currently at 14 as it seemed to fire up better when I increased it. The car runs 24v to the starter motor so it spins over a lot faster. The only thing 12v on the car is the ecu and engine loom wiring

[smokeshow]

Well they do use the same air. Dynamic airflow is almost identical. But I see the issue now...your IAC is only active and trimming airflow in one of those files. Because of that old 'one bit of pedal' issue those old throttle position sensors have. Your idle adapts are frozen in the file that shows 0.4% of throttle position because it is disabling adaptive idle. Oddly enough, it almost looks to run better without idle adaptives lol.

[paulglasper]

Well they do use the same air. Dynamic airflow is almost identical. But I see the issue now...your IAC is only active and trimming airflow in one of those files. Because of that old 'one bit of pedal' issue those old throttle position sensors have. Your idle adapts are frozen in the file that shows 0.4% of throttle position because it is disabling adaptive idle. Oddly enough, it almost looks to run better without idle adaptives lol.

Just had a look and the one where it starts and idles well is the one with throttle sat at 0.4%. Where are you seeing that the adapt is frozen? As both logs show idle adapt (STIT) happening. Just the 0.4 log is adapting a lot less as it?s where the ecu was tuned to. The other log is adding around 9g of airflow to make it idle as the normal good setting is for some reason not enough randomly

[smokeshow]

It's just sort of quivering. The adaptive idle should move that short term error into long term idle trims but it just hangs out. Maybe you have those zeroed out...would have to see your file.

That's definitely a weird looking idle for sure.

[paulglasper]

Yeh I zeroed the LTIT out whilst I was trying to tune in the idle airflow tables better.

Yeh it’s so weird. To me it’s like the IAC is resetting itself into a different position as like you said the dynamic airflow is the same in both logs but the IAC is open a load more so should be higher. So it thinks it’s in a different position but actually it isn’t.

I’ve even tried a spare ecu I had.

I will get new logs tomorrow with what you requested as it’s now midnight here in the uk.