I've had it with the IAC

larry bud · 04-30-04, 09:07 AM

This has to be one of the worst designs ever in a car. I've had this car 12 years, replaced the IAC frequently (it's not cheap!), cleaned the throttle body all the time, set the base idle, checked for vacuum leaks, etc. I'm done. I'm tired of the hunting idle, the occasional stalls, it's ridiculous.

What would the problem be with blocking the port where the IAC rests so NO air can get into it, and just setting the idle with the idle screw? How do other fuel injected cars set idle?

Ken · 04-30-04, 12:41 PM

Something doesn't sound right if you keep having to replace IACs all the time. I personally, have never had a problem with one, and I've had my Vette since '94.

vettepilot · 04-30-04, 01:04 PM

Maybe cleaning the throttle body all the time is the key to the failures. Why does it need cleaning so often, and what are you using to clean it?

Strong solvent type cleaners may be getting onto the pintel (sp?) of the IAC, and damaging it. Aren't those made of a form of plastic, nylon or material of that nature? You could be doing more damage than good with agressive cleaning.

I think all fuel injected engines of the same year grouping probably have similar technology to control the idle.

vettepilot

zog · 04-30-04, 01:19 PM

I agree...there must be something else wrong. My 86 has the original IAC at 102,000 works perfectly...I wish I could help diagnose the problem, but therer has to be something else going on...just makes sense

larry bud · 04-30-04, 01:53 PM

I clean it when the idle goes haywire with Carb cleaner. I remove the IAC before any cleaning takes place. I believe I've put in 4 IAC in 12 years. Seems excessive to me.

I'm also on my 2nd throttle body, this time a BBK. Works great, smooth response.

You guys have never had a roaming idle? The question remains, why do we need the IAC?

vettepilot · 04-30-04, 03:18 PM

Hmmm,
Not sure if I'll be much help to ya, I had a 93 and at 146,000 miles the original IAC was still installed, and had no problems.
I remember reading about the IAC and how careful one had to be when it was out of the throttle body, care had to be taken to not turn the threaded portion.
There was also an idle relearn procedure when installing a new IAC:
Went something like this, start engine let idle for about 10 seconds, then shut off, repeat 3 or 4 times until idle smooth and RPM was consistent. Does that sound right to you?
In respect to your question about if it's needed, I think you probably (in a roundabout way) answered that question already, without it the idle control won't be correct, and hence poor idle characteristics.
Now that brings me to another point, when cleaning the throttle body, it's noted that you removed the IAC to prevent damage, however, I think, (the key word here is think) that there is an air port that the IAC pintel goes into, this is how the idle is controlled. If dirt from the throttle body cleaning runs into that port, it may be restricting the port. Just trying to guess what could be going wrong. That many IAC's having to be replaced just doesn't sound right, I don't believe I have heard of many having to do that.
Also, how were you able to determine that the IAC was bad? Or was it assumed it was bad because of the poor idle characteristics.
Is there a test procedure, if I remember correctly there is a setting measurment of the pintel. At least in the latter years (1993) that I had.

vettepilot

larry bud · 05-03-04, 09:24 AM

I haven't seen any test procedures for the IAC. It doesn't even throw a code, which is interesting that they would design it that way.

I also clean the port out where the pintel rests.