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  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech

idle issues when using AC

  • Thread starter Thread starter hdrunk5
  • Start date Start date Jul 16, 2011
H

hdrunk5

New Member
Sep 1, 2004
12
0
0
Jul 16, 2011
#1
  • Jul 16, 2011
  • #1
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

SN Certified Technician
Aug 14, 2009
5,892
514
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Houston Texas
Jul 16, 2011
#2
  • Jul 16, 2011
  • #2
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.
 
H

hdrunk5

New Member
Sep 1, 2004
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Jul 18, 2011
#3
  • Jul 18, 2011
  • #3
Thank you.
 
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