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Old 07-19-2010, 09:48 PM   #1
Crashsector
Scooby Specialist
 
Member#: 98702
Join Date: Oct 2005
Chapter/Region: MAIC
Location: Annapolistown, MD
Vehicle:
1996 Jeep Cherokee
Green

Default 93 Legacy 2.2L - Stumbling/Wandering Idle, only when A/C is on.

I have a 1993 Legacy 2.2L AWD 5MT. The car runs like a top - 152k miles, doesn't leak or burn a drop of oil.

Turning the A/C on causes the idle to wander from around 300RPM up to 1100RPM or so and everywhere in between. On acceleration the engine stumbles and hesitates noticeably. The harder the stumbling the warmer the air becomes.

Eventually the air becomes very (properly) cold and the stumbling problem ends. This usually seems like it happens when I'm at highway speeds.

As soon as I come back off the highway into stop-and-go the symptoms return.

With the A/C off none of these symptoms exist. Power delivery is smooth and very strong. Turning the A/C off in the middle of a WOT run is literally like flipping a switch - it turns off the stumbling.

I replaced spark plugs, plug wires, PCV, air filter, oil, oil filter, timing belt, and a VERY broken knock sensor. I cleaned the MAF and IACV and load-tested the battery and alternator. Everything was fine.

My main question is would a low refrigerant charge cause these symptoms (the stumbling along with warm air)? I'm wondering if this, or a failing expansion valve, is causing the pressure switch to cut the compressor off and on very quickly creating the symptoms I am experiencing.

I'm trying to get my hands on a set of R12 gauges but it's tricky. I'd appreciate any suggestions as to what else I can look for.

Thanks!

--Andy
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Last edited by Crashsector; 07-20-2010 at 08:26 AM.
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Old 07-21-2010, 10:29 AM   #2
Crashsector
Scooby Specialist
 
Member#: 98702
Join Date: Oct 2005
Chapter/Region: MAIC
Location: Annapolistown, MD
Vehicle:
1996 Jeep Cherokee
Green

Default

I *think* I may have fixed the problem... accidentally.

My money at the moment is on an overcharge.

I was cruising around today, experiencing the same symptoms. I dropped by a friend's shop and he let me borrow his (what he thought were) R12 gauges to see what my A/C system was doing. The low side fitting attached just fine and read around 47 psi... a bit high since it was only 80F out or so.

The high side fitting he had wouldn't fit. I found this out by discharging a 3-4 second long blast of refrigerant and oil, completely accidentally.

I gave up and decided to wait until another time when I had a gauge set that I knew would fit. I noticed throughout the rest of the day the problem was gone.

Took two more trips later in the day and had no problem what so ever. Air is cold, idle is stable, no stumbling. I think an overcharge may have been causing the compressor to resist being rotated, hence what I felt as stumbling. With only 130ish crank HP (new), I'm sure this amount of resistance could have been felt through the drivetrain.

I will report back tomorrow when I'll hopefully have a correct set of gauges, but I hope this fixes it.

--Andy
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