why are my IAC numbers all over the place?

[Warp6]

I tried resetting my IAC by using the throttle screw/TPS method. After every adjustment I would shut the car off, then restart and get to closed loop. The numbers were all over the place. It seems like the most minute move of the throttle blade screw wouldn't show any change on my Direcscan until I shut the car off then restarted it. I could turn the screw 1/10 of a turn and it would jump from 9 to 40. After doing this eleventeen times,I finally got it adjusted to 17 with the TPS at 4.40V. Now, I let the car sit for 15 minutes or so. I restarted the car, let it get to closed-loop and the IAC would say 27. Shut the car off, restart (get to closed loop) and it might drop back to 12. It was different after every restart. I'm going to clean the IAC and IAC bore tomorrow. Any ideas why this is happening?
TIA, Craig

 

[14mins]

I have the same problem. I have changed and cleaned everything. Did the whole spring cleaning plus some. Thanks!

 

[Russ Merritt]

Me too!!! Where's the help!!!

 

[salvageV6]

Vacuum leak? Get out the ether/starting fluid.

Gotta reset with the key for any minor adjustment of the screw.

Car should be warm to 160 too.

 

[Warp6]

need more input...

let's hear more

 

[Russ Merritt]

I found out what my problem was, the car I was working on had a rebuilt eng. The people who built it are huge into circle track race engines. They put a comp 218/218 cam in a STOCK GN. Stock turbo, 36# inj. stock intercooler/dutt, neck, ATR pitbull chip. The car refuses to idle, low vaccum (10-12#) (duhhh I wonder why) I talked the guy into a set of 009"s and a new chip (jay's or reds) Should be all set next weekend

 

[BoostMasterK]

I had a similar problem, mine turned out to be a bad connection in the IAC connector. I tweaked the pins a little and it became MUCH more consistent.

Sounds like you're on the right track by cleaning the bore.

Mike [

 

[Warp6]

I think I found the problem...

I pulled the IAC and cleaned it. I noticed while it was coming out it didn't seem to rotate evenly all the way around. The body didn't rotate evenly as the threaded part. Didn't think a thing about it. (whatever) Upon re-install, as I started putting pressure on the body to tighten, the body broke away from the threads, like it was just barely hanging on. No telling how long it's been like that. I went and bought another IAC from Advance($27 - Sorensen) I got the car up to temp and into closed loop. Wammo- readjusted now it's dead on!

 

[Jeff]

My IAC problem...

I pulled my IAC this week to clean and readjust. I noticed that the cone-shaped end (pintle I think it's called) would not rotate. It was my understanding that this should rotate by hand for adjustment. I went ahead and cleaned and reinstalled it. It seems to hold reasonably well, but still comes up with different settings most of the time, anywhere from 50 to about 5, but normally around 20-30. Is it time for a new one?

Jeff

 

[Warp6]

Jeff, I'd say if you don't have any problems with the idle, I'd leave it alone. Just my opinion. It's not cutting off at stops is it? If the idle is reasonable and "holds it's own" I wouldn't mess with it. My idle got all erratic. That was the reason for my checking the IAC in the first place. It wasn't so bad it would cut off at stops, but it sometimes acted like it might.

 

[Jeff]

unfortunately...too late

I already adjusted the IAC. It was over 100 and fluctuated alot when I started. I messed with it after failing the emissions test and trying to get the car sorted out. I now have the TPS and IAC in shape, but the O2s are all over the place.
I'm now thinking maybe exhaust leak? I sprayed carb cleaner around the intake and TB and didn't detect any vacuum leaks, but vacuum is pretty low.
Jeff