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Sorry. I have seen it called the IAC as well as the Auxiliary Air Valve. I did not know there was a difference. <img src="/forums/images/graemlins/confused.gif" alt="" /> Yes, I mean the Auxiliary Air Valve. The big hose that attaches on the side of the throttle body has strong vacuum at cold start and then the vacuum decreases as the engine/valve heat up.


Ok, I gotcha. Vacuum there would indicate the valve is open. Does it stumble worse when you pinch that off?



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If the MAF sensor was faulty, why would it run perfect once warmed up?


I'm only thinking that there could be an issue with fuel as well, though I think it's not very likely. The ECM runs it richer when cold than when warm. It's possible that the MAF could be an issue, but it's not very likely since it runs fine when warmed up.



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I thought the Thermal Valve only opened to allow additional cool air in when the system starts to get hot, such as when the AC is on? I did not know it has anything to do with cold start.


Doh! Brain fart. You've got it right. The opens to the intake manifold when the water starts to run too hot. That kicks up the fan speed for more cooling. The A/C kick-up is still done through the fast-idle solenoid that the valve feeds.

I'll see if I can add any confusi...er, ideas after I get a chance to browse your previous post.

--Dan