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Idle Air Control (IAC) Valve in Pieces

 
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OffwhiteLS
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PostPosted: Sun Apr 22, 2012 7:52 pm    Post subject:  Idle Air Control (IAC) Valve in Pieces Reply with quote

2003 Impala LS - 3.8L

I removed the IAC valve due to a high engine idle condition. While I was removing the IAC assembly from the intake, I heard something fall into the intake.......the plunger tip.

I then removed the intake duct, the MAF sensor and the MAF screen (cracking/warping the aluminum screen in the process; yes, I did remove the snap ring first). I found the plunger tip of the IAC behind the throttle butterfly. I am concerned that there may be additional pieces that I cannot see. The pieces that I have now are:
- main housing and o-ring
- actuation shaft
- spring
- plunger tip

Does anybody know if there are any other pieces associated with this thing?

Also, what is the downside to running with no MAF screen (assuming that the air filter is always installed properly)?

I'm thinking about using some loc-tite to hold the plunger on the shaft and just re-using this IAC valve. I guess that I don't trust a new one not to fall off either.

Thanks.
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IffyG
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PostPosted: Sun Apr 22, 2012 9:00 pm    Post subject:  Re: Idle Air Control (IAC) Valve in Pieces Reply with quote

It sounds like you got all the pieces. The MAF screen should have caught anything else before it would drop in the engine.

As far as running without it, I wouldn't as you proved it serves the function of blocking foreign matter from entering the engine. I wouldn't run without it.

I would advise you to buy a new IAC, the one you have is totally shot if it is in pieces...

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OffwhiteLS
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PostPosted: Sun Apr 22, 2012 9:56 pm    Post subject:   Reply with quote

Thanks for the quick response. My description of the IAC pieces should have been more clear. The housing is intact; really, the only thing that came loose was the plunger tip. It looks like the plunger tip just came unscrewed from the shaft. The threads are still in good shape. Nothing has fractured/cracked. I was able to pull the spring out when I removed the IAC valve. The plunger tip was the only thing that I had to fish out after removing the MAF screen. I can screw everything back together into original form. I just can't belive that the tip is just screwed on there with no other means of retention. You would think the constant spring pressure would "lock" it in place, like on small engine idle adjustment screws, but apparently it didn't (maybe not a high enough spring load)

On this engine, the MAF screen is upstream from the IAC valve. The IAC valve is actually downstream from the throttle butterfly; so If that plunger comes loose, I don't think there is anything between it and the intake valves.......scary.
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outonthetiles
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PostPosted: Sun Apr 22, 2012 9:58 pm    Post subject:   Reply with quote

The IAC is after the MAF screen, so I doubt it caught anything.

The MAF screen is meant to reduce turbulence in the TB so the MAF can get more accurate readings. I'd leave it, its not causing any restriction.

I'd get a new IAC and call it a day.

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IffyG
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PostPosted: Sun Apr 22, 2012 10:36 pm    Post subject:   Reply with quote

You guys are correct, I had pictured the throttle body incorrectly when I typed my response. Either way, I'd leave the screen in place and get a new IAC. I've never heard of one coming apart in the manner you described.

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OffwhiteLS
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PostPosted: Mon Apr 23, 2012 1:06 am    Post subject:   Reply with quote

Yeah, I wasn't concerned about the screen from a restriction perspective: I would prefer that it stays in there. When I was removing the screen to retrieve the plunger tip, I cracked/warped the screen (like the "honeycomb" split). Now, I'm a little worried about vibration or what-not causing part of the screen to break off and be ingested by the engine. A new one is just over $20, so I guess I'll just tack that on and remember that it's cheaper than a mechanic.

I've never heard of an IAC valve failing in this manner either; I was quite surprised. Hopefully it's rare and a new one will be reliable.

Thanks guys.
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