Challenges setting minimum idle air. - ZR-1 Net Registry Forums

scorp508 · 07-02-2024

I've been chasing a situation where my engine stalls when cold rather easily, as well as when the engine is warm if coming to a quick stop.

According to TunerPro RT my IAC steps were ~60 at idle once the car is warm. This seems a bit higher than others here have suggested it should be.

The first thing I did was remove my IAC and clean the pintle and bore.

Before/after. Yes, the O-Ring was put back even though it isn't in the after shot.
IMG_7703.jpg

IMG_7687.jpg

I then attempted to go through the procedure to set minimum idle air and reset the IAC here: https://zr1.net/forum/showthread.php?t=27764

All was going well, but in step 6 my throttle stop screw was basically already turned in (clockwise) as far as it can go, so my understanding is I have no adjustment left to "lower" the minimum idle air. It was a hex head screw, 8mm I believe. Have any of you had to get a longer screw?

This was after messing around with it a bit trying to back it off. When I started the nut and screw head were both all the way in.

IMG_7693.jpg

Interestingly if I let the engine run the idle would start around 1200 (ECM's commanded desired idle was 850), then start climbing in small increments and slowly run away. In other words, it would start at 1200, then 1250, then 1300, etc. and keep climbing until I killed the engine. Vacuum leak? I don't understand how with the IAC unplugged and the throttle body blades not moving the engine was able to gain so much RPM. The TPS was at 0.53v the whole time. Wondering if I should smoke the intake and look for leaks.

The car does idle dead nuts where the ECM wants it, but was hoping to get IAC counts down and improve this stalling situation.

All ideas are welcome.

07-02-2024	#1
scorp508 Join Date: Jan 2024 Location: Boston, MA Posts: 179	Challenges setting minimum idle air. I've been chasing a situation where my engine stalls when cold rather easily, as well as when the engine is warm if coming to a quick stop. According to TunerPro RT my IAC steps were ~60 at idle once the car is warm. This seems a bit higher than others here have suggested it should be. The first thing I did was remove my IAC and clean the pintle and bore. Before/after. Yes, the O-Ring was put back even though it isn't in the after shot. IMG_7703.jpg IMG_7687.jpg I then attempted to go through the procedure to set minimum idle air and reset the IAC here: https://zr1.net/forum/showthread.php?t=27764 All was going well, but in step 6 my throttle stop screw was basically already turned in (clockwise) as far as it can go, so my understanding is I have no adjustment left to "lower" the minimum idle air. It was a hex head screw, 8mm I believe. Have any of you had to get a longer screw? This was after messing around with it a bit trying to back it off. When I started the nut and screw head were both all the way in. IMG_7693.jpg Interestingly if I let the engine run the idle would start around 1200 (ECM's commanded desired idle was 850), then start climbing in small increments and slowly run away. In other words, it would start at 1200, then 1250, then 1300, etc. and keep climbing until I killed the engine. Vacuum leak? I don't understand how with the IAC unplugged and the throttle body blades not moving the engine was able to gain so much RPM. The TPS was at 0.53v the whole time. Wondering if I should smoke the intake and look for leaks. The car does idle dead nuts where the ECM wants it, but was hoping to get IAC counts down and improve this stalling situation. All ideas are welcome. __________________ 1987: Z51 Coupe, Z51, 4+3, Yellow / Graphite 1994: ZR-1 #150, Admiral Blue / Black 2015: Z06 Coupe, Z07, M7, Arctic White / Red Last edited by scorp508; 07-03-2024 at 11:50 AM.