90Mustangfan

when I start the car, it will idle at 800rpm but when I put on the a/c it drops to 600rpm. Isnt there a sensor that compensates for the a/c and brings back up the idle?

stanglx2002

no the a/c always does that there isnt anything wrong

bmorrisj

the a/c is just creating another load for the engine to run, thats why you burn more gas with teh a/c on... the engine is working harder but your not getting anywhere any faster....

bobby

perfectly normal [8D]

roundman

all of you youngsters are dead wrong about this!!!![:@]
on the 5.0 engine, the IAC is supposed to kick up the idle when the AC clutch is engaged to keep the idle up to properly cool the engine when the AC is ON, so I would suggest you check and clean the IAC valve first to see if this corrects this problem. if it don't, then you need to troubleshoot the wiring between the AC clutch and the ECU to see why the signal ain't getting to the ECU which in turn tells the IAC what to do when the AC is on.

88mustanglx

its only soposed to go down for like a split sec then come back up to what it was right?

Pure5.0

Check your battery and make sure you have proper connections.

Idle drops sometimes because so does voltage and amperage. Clean up the contacts at both points. Even the ground. A positive cable can only carry what a ground cable will allow. So both are equally important.

roundman

more or less, yes.