What exactly is the IAC control passage .. im takeing a wild guess and asumming its the small tube on the runners of my tpi? allso with a problem i had before i found a vacume leak i fixed it but i still had the same problem :T

 

You called it an IAC control passage. I've had experience with an Idle Air Control valve. Some call it IAC solenoid. It's probably the same thing you're talking about. I replaced one on my dad's F-150 (he's driving a chevy now!). It was located on the side of the throttle body; I'm not sure of the location on a tpi setup, but it would most likely be on the throttle body. The problem the truck had was a very high idle. The IAC has a small valve that opens to allow more or less air into the engine at idle; remember at idle the throttle blades (butterflies) are in a closed position. The engine needs a certain amount of air to get through at idle in order to keep the engine running while at the same time keeping the idle smooth. A car is not always idling at sea level,or on a level surface. For that reason the IAC's opening is adjusted by the computer. From what I remember, that is the function of the IAC Valve. You may want to double check to be sure. I could be wrong. Anyway, I hope that I've been of some help.

 

Looked it up to be sure. The IAC Valve opens and closes due to engine load (ie.if the a/c is on, or during cold start up). Engine load will cause a higher idle; so the ecm uses the IAC to let more air in. More fuel is also introduced via the injectors to keep the air/fuel mixture correct.

 

The IAC passage is the little hole from the IAC valve to the throttle body blades... it's how air gets to the IAC valve. Clean the passageway out with "Throttle Body & Intake Cleaner For Fuel Injected Engines" when you get a chance... there's tons of black stuff in there. Just don't spray any into the IAC motor itself!


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-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

do what Tom said.... clean those passages as they can get pretty gunked up. You can clean the IAC itself also if you hold it by the electrical connector and let the pintle hang and just spray the pintle.

The little tubes in between your runners are EGR passages.

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Kevin Irving
85 Trans Am WS-6, 305 TPI, custom burned '86 PROM with '87 "165"ECM, Accel Supercoil & 8.8 Wires, Rapidfire #2 @ .055", MSD 6AL, 1.6:1 Roller tipped rockers, Homemade AFPR, K&N cone, no airbox, Aluminum Driveshaft, Wonderbar, TB Coolant Bypass, Ported Plenum, Descreened MAF, Syclone Fuel Pump, JET Airfoil, Mobil 1 synth in all but transmission.

15.556 @ 86.65mph, Nov 10, 2000.... I know it sucks.. but it will get better!

http://www.geocities.com/transam85tpi/

Member - The Tidewater Trans Am Club, Norfolk VA http://www.geocities.com/ttacva/