A/C kills car
 

Last night I was driving to work with the ac on, when i would come to a stop light the engine would just cut off. It would cut off only after I depress the clutch and put the car on neutral. When I turned the ac off it stopped doing it. After it cut off it started right back up. This started after I disconnected the negative batt. cable for about 3 hrs (I changed my speakers). Also after this batt. thing I have notice the idle is a little off. I'll try to get the computer codes, and clean IAB valve today. Any other suggestions is appricaited?????
Thanks.

I had a problem like this once. It turned out that I had a bad spark plug wire. It was flipping forward and shorting on the header when I would stop, but only under the load of A/C being on.

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351W 89 Mustang GT Convertible

You found out the hard way that you should teach the computer how to idle after disconnecting the battery. Okay, you'll have to disconnect the battery for at least five minutes to kill the Keep-Alive Memory. You might wanna leave a door open just to be sure all the electical energy is drained. Then follow these steps:

-- electrically disconnect the IAB valve
-- put the battery cable back on
-- start your engine, then using a couple of hat pins, a DVOM, and the idle stop screw, adjust the screw until you get 0.95-0.995v across the TPS (that's the green and black wires, I believe).
-- turn off motor and reconnect the IAB valve
-- restart and idle with NO ACCESSORIES ON for about 3 minutes
-- shut down for another 5 minutes
-- restart and turn on every accessory on full blast. For an added smoothness to idle quality, I even have it in gear. This is only if you have an automatic, though.
-- shut it down

Problem should be solved. If not, let us know.

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Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch

Thanks guys I'll diffenitly try that out.

Hey Capri306, when i did the procedure you suggested my engine kept cutting off, it would not stay on with out the IAB valve connected. As soon as I connected back on it would idle, but when I disconnected the IAB valve the car would start for about 3 seconds and cut off.
Also didn't get any codes, it was all clear.