idle issues when using AC

[hdrunk5]

Car is a Prochaged 99 GT. Idols just fine when the AC is not in use. Turn on the AC and the idol dips to the point where it will stall the car sometimes. With the AC on the car feels like its bucking, as though the engine is having trouble turning the compressor. It feels like the engine computer is trying to compensate, (surging idol) at times with the AC on. I can manually feather the throttle with my foot and keep the car from stalling out. Any thoughts? I'm thinking new compressor? Thanks

 

[wmburns]

troubleshoot IAC idle problems 1996-2004

The PCM maintains two IAC idle trim values. AC on and AC off.

If the AC is short cycling, this can prevent the PCM from re-leaning a new AC on trim value. Is the AC short cycling?

It would also be handy to know if the IAC is working at all. Read this for more information about how to trouble shoot IAC problems.

Is your mustang stumbling, dieing at idle or idling rough? - Page 14 - Ford Mustang Forums

It would also be handy to know the IAC duty percent with the AC on and off. Should be between 40-60 percent. Confirm that the IAC duty percent changes when the AC is turn on/off.

If the IAC is working and it's confirmed that the IAC is attempting to compensate, then I would look at possible AC compressor issues.

 

[hdrunk5]

Thank you.