Stalls when using A/C or Defrost

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Nov 1, 2005 | 08:37 PM

PeterM66

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Stalls when using A/C or Defrost

Hello Everyone. It's been a while since I was here. I have a 1990 FSB 5.0 with 5 speed manual trans. My problem is that whenever I turn on the A/C or Defrost the Bronco stalls when running at idle. On the highway the A/C and Defrost work fine, but slow down in traffic or to make a turn and it stalls. This is especiallly fun when turning from a highway down an off-ramp and it stalls. Any ideas?

Nov 1, 2005 | 10:00 PM

greystreak92

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Joined: Sep 2002

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From: Gateway to the West

When was the last time the IAC was cleaned really well? If the computer gives you no error codes during a KOEO or KOER test, the most likely problem is cruddy idle air passeges in the IAC (Idle Air Control solenoid/valve).

Nov 1, 2005 | 10:06 PM

Tazz452

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My 89 was doing the same thing. There is a "solenoid" on the throttle body that increases the idle when the a/c kicks on. Mine was bad. I got the replacement at Autozone. I am not sure what the exact name of it was but I believe that it was either the Idle Air Control (IAC) or Bypass Air Idle Speed Control. It is below and behind the intake "tubes" and has a couple wire plug on it. Page 4-25 if you happen to have a Haynes manual.

Nov 1, 2005 | 10:10 PM

greystreak92

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From: Gateway to the West

Yep, the IAC is sometimes referred to as the BYP-IAS or (Bypass Idle Air Solenoid). Replacement isn't always necessary though. It gets filthy in there and can be cleaned with throttle body cleaner and reinstalled using a new gasket between it and the throttle body.

Nov 2, 2005 | 10:49 PM

bgblktruk

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Joined: Mar 2001

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From: California

Oh by the way where can we get the gasket alone?

Thanks

Mike

Nov 4, 2005 | 01:20 AM

greystreak92

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From: Gateway to the West

You can't....at least not to my knowledge. You can cut a new one from gasket paper which is often cheaper than buying a new pre-cut gasket anyway. You will end up with a LOT of leftover gakset paper but you can always cut thermostat gaskets and more IAC gaskets from it later.