I'm still having idle speed troubles, I reset everything yesterday, got the IAC counts to around 35 at 700 rpms and readj the TPS to .55v. I go driving around and bam, the idle speed to back up to 900-1000rpms in Drive and about 1500 in park, and the IAC counts are around 50-60, yet the programmed idle shows to be 650 on the scanner.
Why isn't the ECM bringing the IAC counts back down to get it to the programmed idle???
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I'm beginning to think the TB is worn, but the blades don't seem to have any play in them, but the idle screw is as far out as I can get it, and if I back it out more than a 1/4 inch, the stop doesn't even touch the screw, and it will not run with the screw out that much at all.
Thanks

 

I almost hate to even say this because i know you're competant....


But you've searched high low and everywhere else for other possible vacuum leaks right?

Also.. because your ecm/scanner says the IAC counts are "X" doesn't mean that the IAC is physically coinciding.

My counts looked respectable when my IAC went bad, I replaced it and everything worked beautiful.

 

Yep, I forgot to mention I looked everywhere for any vacuum leaks, not much vacuum lines to check, just PCV, fuel reg line, MAP hose,brake booster, and whatever is hooked up to the smaller nipple on the pass side TB, which should be the carbon canister but mines not hookedup, just plugged. All the other vac ports are ported and have no vac at idle.
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Well, I chanced it and bought a new IAC valve today, what an expensive part that can be...$100 at the dealer, $60 at the auto store. Anyway, haven't had a chance to put it on yet.
May go ahead and buy a new TB since this was a used unit when I got it and have no idea the mileage/use on it.
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Can the plate shaft be worn enough to make a difference yet not be able to tell by pressing on it by hand some way?

 

I dont think it would cause as drastic of a problem as you have

Try the IAC and go from there

 

Well, brand new AC Delco IAC, and same problem.
I went thru the IAC reset procedure and still, idle screw has to be bottomed out before it will idle with the IAC disconnected, then after connecting it the idle goes way up to 1000+ rpms and IAC count is usually greater than 60.
It also surges alot during light accel from a stop.