noisy IAC

yellowstang1994 · Nov 6, 2007

Are IACs known to eventually become really noisy? I have this really high pitched constant noise coming from my engine bay and it sounds like it's coming from the IAC area. I tried listening closer with a cardboard tube but i'm not 100% positive that it's it. The car seems to run fine, could it be on it's way out? Should I just replace this? Also, are the older IACs from the foxbody compatable with ours, or do I need a foxbody TB? Thanks guys

1TallMF · Nov 6, 2007

The foxbody IAC is different altogether. First thing I'd do is take it off and clean it with some carb or TB cleaner, and see if that helps. I can't see it making the noise itself, its probably a air whistling as its passing-through the throttle body or dirt in it.

HISSIN50 · Nov 6, 2007

For driveway diagnostics, disconnect the electrical connector to the IAC and see if the noise changes.

If you have a hole in your throttleblade, it can make noise.

Stephane's idea is a good one. The IAC is PWM'd, so it could make noise. It would probably be louder when the engine is cold or you have the AC turned on (things that increase the IAC DC).

Good luck.

The O.G. · Nov 6, 2007

my smog pump has a few hoses and clamps..
a clamp on a hose came loose and you would think it was coming from the throttle body area...

just a thought for help

Dino Dino Bambino · Nov 7, 2007

HISSIN50 said:
For driveway diagnostics, disconnect the electrical connector to the IAC and see if the noise changes.

When I do that on my car, the engine dies and it won't start again unless I reconnect the IAC. My Summit Racing 75mm TB has one adjustment screw for the throttle blade on the side and a second larger adjustment screw on the top for something else. Do I need to adjust either one of them?
When the tranny's in Park, the idle speed is 800rpm but it'll sometimes drop suddenly to 600. When in Drive, the idle is 600rpm and it'll sometimes drop suddenly to 500 making the car shake. I removed my IAC to clean it but it was already squeaky clean when I looked inside, so I think it may just be faulty. Would you agree?

HISSIN50 · Nov 7, 2007

Bullitt95 said:
When I do that on my car, the engine dies and it won't start again unless I reconnect the IAC. My Summit Racing 75mm TB has one adjustment screw for the throttle blade on the side and a second larger adjustment screw on the top for something else. Do I need to adjust either one of them?
When the tranny's in Park, the idle speed is 800rpm but it'll sometimes drop suddenly to 600. When in Drive, the idle is 600rpm and it'll sometimes drop suddenly to 500 making the car shake. I removed my IAC to clean it but it was already squeaky clean when I looked inside, so I think it may just be faulty. Would you agree?

Yep - you have to hold the throttle open a little when disco'ing the IAC.

You can adjust either the idle bleeder or make a mechanical adjustment to raise the idle (I had a similar issue as you - my volts would drop and the alt light would come on because the idle dropped so far). I ran the idle bleed out to 1.75 turns (from seated. Any more causes a vacuum-leak like symptom). Then I raised the idle with the throttle stop. This was a good band-aid (A very kind member on here burned me a chip and one change was to raise my commanded idle. This fixed the issue correctly).

You might find that the low idle comes from something else and your IAC is actually fine. Enter band-aid solution or scalar changes.

Good luck.

Dino Dino Bambino · Nov 8, 2007

It's not a constant low idle. Most of the time the idle is normal but it'll intermittently drop for a few milliseconds and then return to normal. I'll try your bandaid tricks but I don't think the solution will be as simple as that.

HISSIN50 · Nov 8, 2007

Bullitt95 said:
It's not a constant low idle. Most of the time the idle is normal but it'll intermittently drop for a few milliseconds and then return to normal. I'll try your bandaid tricks but I don't think the solution will be as simple as that.

That's how mine was too. Most of the time it was fine but upon occasion, it would go loo-loo on me. In my case, the clock, radio and something else (cant remember) would shut off when it happened. If I threw it a rev, it would fix itself.

I later went back to a stock setting (like it was when it would act-up) but now I had a stock MAF on there. Guess what - no more issue. Correlation is not causation, but I had a little feeling that the meter could have had an effect on it.

The band-aid should atleast work for awhile for you (I've had about 10 folks contact me about doing this band-aid fix and it's worked for all but one of them).

Good luck.

Dino Dino Bambino · Nov 9, 2007

Thanks Hissin. I'll give it a try.

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