ECM interactions

[rsicard]

Gentlemen:

I have a 16197427 ECM running a 350 Vortec. The RPM at idle when warming up varies according to retarded to ATDC IGN timing, BPW, IAC wherein monitoring the WBO2 goes from 12-13 to near 20:1 AFR and then the ECM and engine recover and then it does it repeatedly. Is there some explanation of the engine parameter interactions on the part of the ECM reactions? Trying to sort this one out. Need to disable some parameter to help sort this out? Need help. Please advise. Thanks.

[dave w]

I think your injector offsets are worth looking into?

It's possible the injectors are going in / out of Async?

I wonder the IAC is doing during warmup?

I would look at the bitmasks when playing back a recorded data log and look at Async and the IAC.

dave w

[rsicard]

I think your injector offsets are worth looking into?

It's possible the injectors are going in / out of Async?

I wonder the IAC is doing during warmup?

I would look at the bitmasks when playing back a recorded data log and look at Async and the IAC.

dave w

Thanks for the reply. Can't get a grasp on Async versus sync mode. Is Async both injectors firing at the same time, whereas sync is batch firing the injectors, 4 on one bank then the opposite injector with the other bank of 4 cylinders. Was under the impression that TBI fires one injector for one bank and the other injector for the other bank. Maybe misunderstanding and need more education. Read up on IAC on this site. Please do not assume I am an expert with this GM EFI stuff. Will go back and replay some recordings and look at IAC counts and sync/Async mode indication and see what correlations with other parameters can be made to gain knowledge about what is going on. Would like to know general ECM inter-relationships of spark, IAC and fuel. Ignition timing on this 350 Vortec ECM has no relationship with that read off the balancer/timing pointer. Know the basics of establishing #1 TDC and pointer calibration. Fairly certain these are OK.

Any more help here would be greatly appreciated. Still learning the ropes. Please advise. Thanks.

[dave w]

Async vs. Sync fueling: http://www.gearhead-efi.com/Fuel-Inj...Asynch-fueling

dave w