My 1992 F 150 302 surges at idle when the air-conditioner compressor kicks on and the the voltmeter goes down about 4 volts. (i.e. the rpms fall about 300 rpm and then return to normal after about 5 seconds). It is not noticable at speed. When I turn off the air conditioner it dosen't surge .
Could it be the IDLER AIR CONTROL VALVE????
Please advise.
Thanks,
92onefifty

 

Could be. I would first try and reset the pcm. Disconnect the neg cable from the battery for five minutes then hook it up, start the engine, allow the idle to stabilize then turn on the a/c, put the truck in gear(all while at idle), then take it out of gear. This will allow the pcm to relearn its idle strategy. But, before you do this, disconnect the idle air control and see if the engine will just barely stay running(approx 500 rpms). If not, adjust the throttle screw until it does, then plug in the IAC.

 

My 97 5.4 is doing the same thing. Replaced the IAC but it didn't help. I'm searching these threads for another solution. Good luck!