Hey guys,
I got a phone call today from a workshop I do some work for from time to time. I never really know what they have in store as its always something different. Car in question VT SS, 346 forged internals, 238-244-110 cam. I built a base tune for it and got the maiden start on it once I got it to 80 deg C I started logging IAC counts there at 140 timing around 20-25 degrees, Idling initially at 1000rpm, It idled decent very choppy from lots of overlap. It has a FAST cable 92 mm TB fitted.
What was happening was at times the idle timing controls would cease working i would press the pedal a few times and they started working again, It was not going into the idle tables. The aftermarket TB hadn't been setup. The IAC counts are fairly high I need to adjust the screw and redo the airflow tables.
I figured as the TPS was reading 0% that it should be in idle mode. Due to it being intermittent I am thinking possibly the voltage was to high on the tps at idle and after i adjust the screw and get the iac steps around 50 I can reset the tps and check the voltage again.
Another thing I noticed was the startup was effected sometimes it fired straight up and others it didnt Im thinking it is due to the pcm not using the idle tables at startup after it did start it was idling on the high timing table, i would shut it down play with the pedal and get it to fire first kick and coincidently it would be using the idle timing map with timing correction making changes.
I am confident this is the problem, I really would like to be down there now tinkering but will have to wait till the morning. This is the first time I have encountered this with the FAST even without calibrating the TPS.
Has anyone had similiar experiences?
Cheers
Joel