Another Idle Problem

Sketchy_GT

Active Member
Nov 13, 2016
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So I was idling in the drive thru the other night and i noticed the idle was fluctuating it would drop down and sound like it might die then it would idle back up to normal. but probably every 30 seconds it would do that. i know the car needs plugs i can feel a slight miss when driving so im going to do plugs this evening and hope it helps, any ideas (99 Mustang GT 99,000)
 
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wmburns

SN Certified Technician
Aug 14, 2009
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505
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Houston Texas
Just wondering. Was the AC on? Is your AC low on Freon (short cycling)?

Note, if the AC is short cycling this prevents the PCM from re-learning new "AC on" idle trim values. EXPECT idle problems when the AC is on.

One way around this might be to jump the AC low pressure switch with the motor idling at full operating temperature for 3 minutes. Do not leave the jumper connected for extended periods of time or the coil will freeze.
 

Sketchy_GT

Active Member
Nov 13, 2016
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Found 6 dry rotted coil packs and FACTORY spark plugs so im gonna start from there