Ok, please be gentle, kinda new here. I searched and couldn't quite find a similar case so here goes: I've got a 4x4 with a 351 modified Ford engine that I installed a TBI system on - had it left over from a previous project (89Chev K1500 5.7) I installed all components except the VSS - still working on a way to adapt a Ford VSS signal to the gm ECU. Running a Moates Ostrich, 1227747 ECU, ASDU Bin that I've got set up to run pretty well - the only issue I can't seem to beat is idle. It will start and idle ok when cold, warm up and usually settle down to the 800 RPM I've set it to. I do have the VSS required for idle set to 0 since I'm not giving it a VSS signal. The IAC park position is 145, TPS for idle is 1.17 V (actual idle voltage is 0.80V - if it's under threshold it thinks it's at idle, right?) I also have the VSS flag turned off to avoid a check engine light. It will randomly decide to idle at 1500 or so RPM once warmed up. I have a P/N switch hooked up and verified is working through the data on my scanner. When it goes up to high idle it doesn't matter if it is park or not (except out of gear it will flare up to 1700 then settle to 1500. The IAC counts are around 15 at low (proper) idle and closer to 45-50 when it takes off; which leads me to believe this is a software/tuning issue as the ECM is asking for more IAC counts as opposed to a vacuum leak (which wouldn't come and go) The other day I was out rockcrawling all day and it idled high - then shut it off, restarted it and drove 10 kms back to town where at the first red light I caught it settled back down to 750 or in gear.
I won't lie, I don't know how to data log as I always use my snap on scanner which does it for me (mechanic by trade) If anyone has any ideas, please let me know. I've found numerous postings online about how to set up the various IAC parameters, but nothing I've tried has helped. Thanks for any help; if anyone needs more info, let me know.
Weird TBI idle issue on Ford swap
Moderators: robertisaar, dex