TBI Swapped Ford 351M - Hi Idle Issues after in gear

[Speedyzee]

Hey Dave; I thought about the lack of VSS a few times - but I have set any tune values to 0 as far as throttle follower steps, MPH to enable Idle or large IAC error etc.
Not discounting anyone's thoughts, but riddle me this: what it does is - Truck in Park, idling - closed loop, holding desired idle RPM in park (IAC counts around 18 = 750 RPM) - pull it into gear and let the ECU raise IAC counts to get back to desired CL idle RPM (Now prob 34 counts to get back to 750 RPM) I put it back into Park (yes ony - P/N switch works and I can see it change state with my scanner) and then the idle seems to hang at anywhere from 950-1000 RPM - the IAC counts are higher than at desired RPM (usually stay at 34-ish), so the ECU is commanding the new idle speed; since I haven't moved the truck, a VSS signal shouldn't matter - otherwise a stock GM TBI would act the same way if you pulled it into gear, idled for a few seconds sitting still and put it back into park, right?
I did find a scaler in the tune labelled Min TPS % which was set at 25% - now that I'm at 0.50V TPS at idle that puts me at 10% - I changed the value to 10% and will see what happens tomorrow. Thanks for any and all suggestions so far... I wouldn't give a rats a** about the idle issue if it wasn't for the truck having a doubler transfer case with a redic amount of gear reduction, and my tendency to flop the thing on it's side from time to time on the rocks. A nice predictable low idle would be very nice :)

[dave w]

Hey Dave; I thought about the lack of VSS a few times - but I have set any tune values to 0 as far as throttle follower steps, MPH to enable Idle or large IAC error etc.
Not discounting anyone's thoughts, but riddle me this: what it does is - Truck in Park, idling - closed loop, holding desired idle RPM in park (IAC counts around 18 = 750 RPM) - pull it into gear and let the ECU raise IAC counts to get back to desired CL idle RPM (Now prob 34 counts to get back to 750 RPM) I put it back into Park (yes ony - P/N switch works and I can see it change state with my scanner) and then the idle seems to hang at anywhere from 950-1000 RPM - the IAC counts are higher than at desired RPM (usually stay at 34-ish), so the ECU is commanding the new idle speed; since I haven't moved the truck, a VSS signal shouldn't matter - otherwise a stock GM TBI would act the same way if you pulled it into gear, idled for a few seconds sitting still and put it back into park, right?
I did find a scaler in the tune labelled Min TPS % which was set at 25% - now that I'm at 0.50V TPS at idle that puts me at 10% - I changed the value to 10% and will see what happens tomorrow. Thanks for any and all suggestions so far... I wouldn't give a rats a** about the idle issue if it wasn't for the truck having a doubler transfer case with a redic amount of gear reduction, and my tendency to flop the thing on it's side from time to time on the rocks. A nice predictable low idle would be very nice :)

I'll answer your riddle with a riddle. Why did the spark advance change in your experiment "when the VSS signal shouldn't matter"?

dave w

[myburb]

I haven't used that ecm so this is just a wild guess. Could it be with no vss connected the unknown internal logic thinks when you put it in gear it moves to moving vss logic and stays there until the key is cycled.

[ony]

some where if you search this sight there was a man in germany with about the same conversion,can't think of his handle.might find something he learned I think he had this problem too.