High idle on cold start: vacuum leak or IAC setup?

[opethmike]

That sounds about right. Putting an auto in park will drop the idle usually around 200 RPM or so. That could also be why you are stalling on lift; throttle plate closing too far. Not saying it is for sure, but it ain't helping.

[jangell]

I do have MS set to closed loop. You'd think that it would open the IAC to get the idle up to 790. I probably have something set up wrong if I was seeing ~650 when in gear. I also don't know how fast the IAC can react -- it might be too slow to account for the rapid change in MAP from tapping and releasing the throttle, perhaps?

I'll open the screw a bit, raise the idle, and see if it still stalls out on me. And go over the TunerStudio settings again. Thanks!

-- Joe

[FABombjoy]

The spastic TPS is a problem - per your tune settings, closed-loop idle won't activate until TPS is less than 1%. RPM drops but the stepper valve never opens. You may just need to further open the base idle to compensate a little until you have TPS working.

Or set the threshold for idle activation higher than your stuck TPS value and tweak the RPMdot and load values so it activates only when your likely to be idling.

[jangell]

I keep forgetting that TPS is used in places like that. That would explain a lot.

I went to the junkyard and got a TPS off of an actual Mustang, and of course it doesn’t fit (slightly different mating size for the barrel, slightly different screw hole spacing). I should have trusted that’s Josh had the right TPS in the first place. I put the old TPS back in with a much thicker O-ring, and it seems to be working OK for the moment. We’ll see if that lasts.

I was still getting the idle dropping to the 650 range until I changed Use Last Value it Table to Table and configured a basic table. Now it soft lands around 790 RPM like I want it to.

I think I have the decel and idle sorted well enough for now. Next is to figure out why it wants to stall when I open up the throttle even a little quickly. Probably time to play with accel enrichment and the VE table, or something.

Thanks!

— Joe

[opethmike]

I keep forgetting that TPS is used in places like that. That would explain a lot.

I went to the junkyard and got a TPS off of an actual Mustang, and of course it doesn’t fit (slightly different mating size for the barrel, slightly different screw hole spacing). I should have trusted that’s Josh had the right TPS in the first place. I put the old TPS back in with a much thicker O-ring, and it seems to be working OK for the moment. We’ll see if that lasts.

I was still getting the idle dropping to the 650 range until I changed Use Last Value it Table to Table and configured a basic table. Now it soft lands around 790 RPM like I want it to.

I think I have the decel and idle sorted well enough for now. Next is to figure out why it wants to stall when I open up the throttle even a little quickly. Probably time to play with accel enrichment and the VE table, or something.

Thanks!

— Joe

Definitely AE, not VE. For this particular issue, leave the VE alone.

[jangell]

Will do — thanks. I’m using a clean, untuned VE, so I need to get to auto-tuning as well.

I drove around the block. Got a few stalls on acceleration, as expected. The idle also dropped to >650, because apparently the TPS got stuck again (this time at 5.5%). <sigh> Guess I’ll tinker with that for a bit, but I’m getting closer to just unplugging it and switching everything to MAP.

— Joe

[jangell]

I’m giving up on the TPS and have disabled it (unplugged the connector and jumped ground and sense), then set up MAP AE, and it revs fine now without stalling out. It’s getting dark soon, so I’ll do another drive tomorrow. Also, I need to tighten the belt, and it’ll be nicer to do that without risking burns from the exhaust.

Thanks again!

— Joe