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So I have a 1993 Bronco with a 5.8 liter engine. Every time I start is up it runs fine if the A/C is off. If I turn the vents on or any air conditioning for that matter the idle drops and if I don't give it gas it will die.... What is wrong do I just need to adjust the idle? it also does this if I put it in reverse. The only engine problems its had is the eec went out and had to put new capacitors in. Please help might be a dumb question but gotta ask!:thumbup
 

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I would assume the computer should kick up the rpm's when the AC is activated. I would search for that and see if maybe there is a bad sensor or switch or wire.

Just ideas. The MSD Atomic I installed on my 1979 with a 460 has a AC kickup, it attaches to the wire that goes to the compressor and when the compressor kicks on it kicks up the rpms through the trottle body to compensate.
 

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The IAC (Idle Air Controller) is responsible for engine idle. The EEC should command the IAC to open/close as necessary. So, first try and clean up the IAC, and if you decide to replace it, get a Motorcraft. I went through 3 IACs from two different vendors before I bought a Motorcraft IAC.
For reference, the EEC has four idle modes: A/C on in Neutral/Park, A/C on in Drive, A/C off in Neutral/Park, A/C off in Drive. If you clean the IAC, or replace it, disconnect the battery to clear the EEC's IAC settings, and after you get it back together, make sure you go through the four modes above (give it a minute or so in each mode).

And do what Steve83 says too!

Good Luck
 

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Actually, it's only responsible for the amount of air going in at idle. The EEC is responsible for idle (and all other modes), and it also uses fuel injector pulsewidth & ignition timing to regulate the idle speed, based on inputs from almost every other sensor.

The IAC is responsible for more than just the air at idle:



If you don't know the answer, make something up, say it loud, and some people will believe you.
 
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