96 Chevy C1500 4.3

So I took off and cleaned my EGR and IACV with some carb cleaner, also sprayed some at the TB and wiped it down and finally I replaced the PCV. When I finished and started it up, the idle shot up to almost 3k. If you leave it running, it will drop down slightly, but still over 2k. Also, it is making a loud hissing sound from the TB or around it. All gaskets from the head up have been recently changed, but prior to these cleanings. So I don't believe it is a I'M or TB gasket.

I can't find a vacuum leak and EGR/PCV wouldn't raise an idle that high, I don't think. So TB/IACV? What else? Or how can I test them?

 

Oh, and the idle goes back to normal if shifted into gear. The high idle is only present in park and neutral..

 

After some research I am getting some conflicting info about the IACV. I am reading from some people that the pintle has to be adjusted before reinstalling, and others saying it does not matter the computer will relearn and adjust as needed. I moved the pintle quite abit when cleaning and am pretty sure it didn't go in the way it came out... And even though I don't have anything to compare it to, I was going to pull it out and adjust it slightly to see if it even makes a difference. Sadly I stripped out one of the bolts (Doh!) when doing this, so now I have to remove that somehow before proceeding...

Could that be the cause of the high idle? I find it crazy the the engine even gets enough air to hit 3k+ with the TB butterfly closed and only the idle hole open...

Oh, and yes I did try pulled the negative terminal for 15 mins, no change. And if I unplug the IACV, the idle slowly goes up. If that helps any...

 

Here you go


http://www.fullsizechevy.com/forum/g...e-toolbox.html

 

Good post, I am bookmarking that.. yet that is just a list of performance mods basically A short how-to on cleaning the IACV but it doesn't say anything a high idle.

Although I didn't jumper mine, I just pulled it out as far as I could, are you saying that is the problem?

 

But it tells you how to put the pintle back correctly which could deffinitly affect the idle.

 

Ok gotcha, so the pintle position, when reinstalling, can cause an idle that high. Well I will try that procedure and see what happens.

 

If anyone was watching this with a similar issue, or just for the archives, here was my problem:

I took the TB off completely to examine things closely aswell as a more thorough cleaning. Well, with the TB in my hands, I noticed that the IACV was not bolted on straight, it was slightly crooked and the pintle was pushing into the TB wall (leaving the port almost completely open). So I unbolted the IACV, cleaned the TB thoroughly, and reinstalled the IACV back in. It's a snug fit and it takes a little wiggling before it sits flush. It is almost impossible to tell if it's flush on the truck, so be careful if you do not remove the TB.... Reinstalled, and the truck is idling normally again.

Edit: As far as I can tell, pintle position upon reinstall really doesn't matter. I bolted it on, turned the key on for 20 seconds, off for 10, then started it and the idle was dead on. (Even though I still didn't adjust the pintle while it was out.)