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Discussion Starter #1 (Edited by Moderator)
A post by Green91 made me realize that I had a problem with my IAC valve - it didn't cause the engine to stumble when you unplugged it. Come to think of it, the revs would sometimes hang up, when I'd shift. I figured that the valve itself was not closing fully(or enough). So I tried the valve which I'd kept off of my junker E250 4.9, and it didn't seal any better.

I had to swap the 4.9 IAC valve onto the 'Stang's IAC motor, as the 5.0 harness wouldn't reach. I noticed that when I had the valves separated from the IAC motors(actually, I think they're "plunger" solenoids), that the valves would seal better. (Where the valve mates to the intake, there are two holes. I tried blowing through the hole farthest from the IAC motor.) I noticed that as you fit the IAC motor to the IAC valve, that the valve pintle began to unseat. Well, I then thought, "why not install a spacer between the valve and the IAC motor?"

So I took a choke-bimetal housing gasket(the solid round one) from a carburator rebuild kit, and cut it to fit between the IAC motor and valve. I did not reuse the original O-ring with the gasket, as it caused the two pieces to not mate up properly. With the gasket between the motor and valve, I could not blow as much air through the valve as before. (I don't think the IAC is supposed to be totally airtight when closed - but I really don't know.) I also swabbed a little 3in1 oil into the motor, to lube the plunger. I put it back on the car, and it idled and ran kind of crappily for a few days, but now, it's running alot better. I haven't had the revs hang up for a couple of days now, and the engine definitely stumbles when you unplug the IAC. It still idles nice and steady too.

In conclusion, I think that spacers between the IAC motor and IAC valve may be a cheap easy fix for a valve which doesn't seal as well as it once did, and perhaps, an alternative to that adjustable piece you can buy, which fastens between the IAC and the intake manifold. The only bad thing is that sometimes those screws, which fasten the IAC motor to the valve, can be quite tough to loosen - I had to use vice-grips on the ones on the E250 piece.
What can I say? I'm a skinflint hack!!! Afterall, who wants to spend money on an IAC valve?
 

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Your computer was used to the IAC valve not helping anything.
 

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Discussion Starter #3
Yup, it's important to give the computer time to learn how to run the motor, when changes, like this, have been made. It actually almost stalled a few times, when I went to stop, the first day or two, after I did this.
 
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