cliffyk

I was a bit bored this afternoon so I decided to dissect my old IAC to see what about it's design would make it "honk like a goose"/"sound like a French horn" toward the end of its service life. I and a couple other members have experienced this and I really wanted to understand why.

Toward that end, here's what the IAC looks like inside (the solenoid motor is not shown):



The valve plunger is supported and centered on four vanes at the end of its body--I believe that as these vanes wear the valve plunger becomes free to chatter from side-to-side in the bore beneath the valve seat.

When these oscillations reach an amplitude and frequency to which the intake tubing, back through the air box, is sympathetic the whole thing behaves as a wind instrument and produces the rather loud tone I and others have observed.

This process is quite similar to the manner in which a goose honks, or a French horn works, so it is not surprising that they sound much the same.

I see no fix for this other than replacing the IAC...

black35th

Interesting. I've always wondered what they looked like on the inside.

At the same time, it really makes me sick knowing how much they charge for those. There is really nothing to it.

SVTeeshirt

thats pretty awesome.

huey_33

Now that you mention it, I have the dreaded "goose honk/french horn" on my car. Cliffy, when your car was making the sound, was it just at acceleration or at all times? Mine does it every once in a while but only under slight acceleration, like when I barely touch the gas pedal to creep forward. But for some strange reason it sounds like it's coming from the back of my car.

cliffyk

Those are the situations under which mine made the noise--a quick "blip" of the throttle would clear it at first, then it got more persistent--a new IAC made it go away...

Chumley

Cliff, Thank you. You nailed it. I've been trying to figure this out for ever. It must have been bad from the factory.

school boy

ive almost done this to 1 of my 3 lyeing around the garage but like someone said about the cost pervented me from doing it!

1998Slow 'Stang

Good job finding a year old thread

cliffyk

I directed Chumley to it yesterday--that aside and though it was not that way herein, we like to encourage people to use the search function, not deride them if and when they do...

FLMustangMan

I wonder if this is what is going on with my car. I am already have idleing issues now and again but i do have a noise that only occurs through lite throttle. If you see my video on my old post about 96 GT ticking noise, let me know if this was anything similar to what you have heard Cliffy. I'm at work and cant add that to this? Did it ever go away/quiet down as the car warmed up/driving more than 15-20mins.