I tried it all. Ripped up the plenum, tore off the runners, put carb cleaner and propane everywhere..and nothing!! I cant find this loud vacuum sucking sound. I once heard that a bad IAC stuck open or closed will produce this sound. Anyone hear of that or had any experience with this PITA? Im afraid to drive it cause i dont want to lean any cylinders out because its all totally new. BTW, its a 355 tpi,MAF, 52mm throttle body, edelbrock runners and base, tfs heads, headers, rockers, cam, yada, yada, yada. Thanks in advance guys.

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"Ever notice how imports sound like weedwackers"

 

I dont know about a loud sucking sound, but when my IAC went bad my car would not run once it warmed up, it would die every time it was put in gear above like 120*

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90 IROC 5.7l (L98)
ram air, K&N's, air foil,Flows

 

YES! A stuck open IAC will make a loud, violent sucking sound almost sounding like a supercharger. Hehehe

Mine 92 Z did that. All I did was take the IAC housing apart and cleaning everything in there. Didnt have a problem after that.

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92 Z28 L98 350
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Ported and polished heads, ported stock TPI base, ported plenum, Comp Cams XR270HR-10 cam (lift .495/.502 duration 218/224 lobe separation 110), Edelbrock TES headers, LT4 valve springs, Crane AFPR, Flowmaster catback with LT1 style tips, MSD coil & wires...

"Take that auto, drop it in first, hold the brakes, stomp the gas and grin from ear to ear! :-)

 

FG,

Rumor has it that almost all Edelbrock/BBK throttle bodies make lots of noise through the IAC air ports because the design doesn't muffle the sound like the Rochester TBs do.

If you are concerned about being lean, check the oxygen sensor output or use the ECM in Field Service mode to see if the ECM is correcting for a lean condition.

If your IAC were leaking that much air, the idle should be way over stock target idle.

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Later,
Vader
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"Make Me Bad"
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