Engine running rough when AC is on.

SONYAMARIETX

MEMBER
2005 FORD MUSTANG
142,000 MILES

Had the fan replaced 2 years ago, being the engine would start running really rough, would turn off car and restart, the engine would some how reset and run fine for a few minutes. Had the problem checked was the fan going out. Somehow the computer shuts the engine down. Now having same issue when I turn on the AC, the engine runs rough and makes a noise with hardly any power. But when I shut off and restart, it runs fine, till I put AC back on? Any thoughts?

Tuesday, June 18th, 2013 AT 2:10 PM

3 Replies

CJ MEDEVAC

MECHANIC
11,005 POSTS

THIS SOUNDS LIKE THE A/C COMPRESSOR IS LOCKED UP

AS LONG AS THE A/C CLUTCH IS NOT ENGAGED, THE PULLEY TURNS FREELY

WHEN YOU ENGAGE THE A/C (OR ANY HEAT MODE THAT INCLUDES "DEFROST"---"DEFROST" MODES MAKE THE COMPRESSOR ENGAGE TOO). WHAT IS PROBABLY HAPPENING IS THE COMPRESSOR CANNOT TURN, IT'S PULLEY SITS STILL AND THE BELT WILL NOT ROLL OVER THE PULLEY, THIS FRICTION INSTANTLY BOGS DOWN THE MOTOR

HAVE SOMEONE WATCH THE A/C PULLEY AS YOU ENGAGE THE A/C TO VERIFY MY HYPOTHESIS

RETURN WITH NEWS

THE MEDIC

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Wednesday, June 19th, 2013 AT 8:42 PM

SONYAMARIETX

MEMBER
2 POSTS

HI,
Had everything checked. A/c compressor was perfect, pulley's fine. Turned out to be a few bad ignition coils. Had plugs replaced last year, didn't replace coils. So replaced all 8 and running great.

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Monday, July 1st, 2013 AT 10:30 AM

CJ MEDEVAC