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Sep 17, 2011 | 11:17 AM

bpounds

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From: Whittier, CA

IAC experts question

How does this IAC look? This is off the truck on the bench. In the first pic you can see the valve is cracked open a bit. This is how it was when I pulled it off the truck. In the second pic I have pulled it back a little with my fingernail, and as you can see the spring does not close it. I guess I expect a spring loaded valve to be closed normally.

This valve has about 35k miles on it since it was changed. The truck has 117k on it. It is running okay, and starts okay, but does not snap to life like it has in the past.

Sep 17, 2011 | 11:28 AM

barthel

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From: Newberry Springs, CA

Bill,

Mine looked and acted exactly like yours when I pulled it off. After I cleaned it and put it back on it worked fine. I guess as long as the spring is working you're good.

Sep 17, 2011 | 04:53 PM

SpringerPop

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From: La La Land

What's with the spring loading?

IACs are usually driven open and closed by a jackscrew driven by a stepper motor.

Dunno'....

Pop

Sep 17, 2011 | 07:10 PM

bpounds

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From: Whittier, CA

Thanks for the comments. I cleaned it up, even though it was very clean for 35k miles, and put it back in. It seems fine, but the stumbling start was so occasional that I doubt we will notice anything changing.

Pop, the bonnet floats on the shaft, and feels like it is opposed by a spring. And on the closed end there is a spring that is probably just an end of stroke cushion. So I was guessing it is a linear servo. Only a guess.

I cleaned up the throttle body with some carb cleaner, fixed my cruise control cable, and all seems well.

Need a new battery sometime before winter.

Sep 17, 2011 | 09:25 PM

SpringerPop

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From: La La Land

Four wires to the valve?

If so, likely that's a stepper.

Pop

Sep 18, 2011 | 10:42 AM

bpounds

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From: Whittier, CA

Only 2 wires, Pop. Which means it is simply a solenoid valve. Which also means there is no feedback, which is why a failed/dirty IAC rarely sets a fault.

Sep 18, 2011 | 10:01 PM

SpringerPop

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From: La La Land

Well, the "feedback" is sensing the RPM, but you've got the operation nailed, Bill. Two wires equals simple solenoid or DC motor with polarity reversal.

Pop