IAC pegging at 175. Won't idle.

[urhstry]

What can cause this? 3 different IAC's, reset them all about 6 times. I do have that 45 degree piece on the TB. Could that be causing it? Thanks guys.

 

[urhstry]

Ttt

 

[Blazer406]

What can cause this? 3 different IAC's, reset them all about 6 times. I do have that 45 degree piece on the TB. Could that be causing it? Thanks guys.

Need more info.....

When you reset the IAC.... did you follow the accepted procedure here:

IAC Reset Procedure

Could you have some sort of blockage in the IAC passages preventing it from bypassing air.... like an overhung gasket or something?

What is your TPS voltage at idle?

 

[urhstry]

Yes, the IAC procedure was followed from the Gnttype site. Never had a problem until I just rebuilt the engine and put it all back together. No blockages that I can see. Brand new 45 degree IAC repositioner on the TB. TPS is at .44. ?????

 

[Blazer406]

resetting the IAC

So..... are you saying that you were able to reset the IAC..... like down to 20..... and at some point later... it goes back up to 175.... by itself?

 

[urhstry]

Well it's random. At start up I look at the scanmaster and see anything from 45 to 130...and in short time it goes up to 175. Won't idle and if it does, it hangs around 450-500RPM, choking. I don't think resetting the IAC does anything.
I grounded the ALDL and checked the 4 prongs with a test light and found all four to have power, which according to Mitchell, means there is a faulty IAC connection or IAC valve. 3 valves later, same thing so now I am thinking the wiring is screwed up somehow. Changed the ECM also and different chips. No difference.

 

[chris2316]

i tried that iac procedure , i didnt have good results either ! what i did is started the car to see if it wanted to die if it did i shut it off turned up the idle screw ever so slightly and tried it again til it idled ! that procedure i believe is for stock cars with stock cams , not really for cars with cams like i have ! im having no issues doing it my way ,,,,,good luck

 

[chris2316]

oh i forgot to tell you every time you adjust the idle up or down you have to reset the t.p.s!

 

[TurboDave]

Well it's random. At start up I look at the scanmaster and see anything from 45 to 130...and in short time it goes up to 175. Won't idle and if it does, it hangs around 450-500RPM, choking. I don't think resetting the IAC does anything.
I grounded the ALDL and checked the 4 prongs with a test light and found all four to have power, which according to Mitchell, means there is a faulty IAC connection or IAC valve. 3 valves later, same thing so now I am thinking the wiring is screwed up somehow. Changed the ECM also and different chips. No difference.

What your symptoms are saying is: The ECM is trying to keep the engine rpm at what's commanded. However, for some reason the engine rpm are dropping below what the ECM is trying to set, hence the IAC numbers that keep increasing. The rpm drops to a level low enough that the IAC is maxed out and cant introduce any more air and the rpm is still dropping (chocking as you call it). My guess would be that the throttle plate's minimum air setting is maybe whacked, and the throttle plate set wrong.

Instead of messing with that stupid and useless reset procedure (that does nothing more than get unsuspecting folks in trouble). Have you tried turning the minimum air bleed screw CW a few turns? How is it set now? is the tip of the screw touching the throttle stop plate?

 

[urhstry]

ok, here's an update. I took the throttle body off and found the throttle plate to be touching/scraping the side. Must have moved somehow. I recentered the plate and tightened it up. Ran out of beer so we'll see what happens today. Good call Dave.

 

[urhstry]

Yep, that was the problem. And you were correct Chris. I had to adjust the idle screw in quite a bit more than with my stock setup to get it to idle just right. Thanks for all your help.