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Q: When the car is stopped and in gear, the engine often shakes and nearly stalls when the air conditioner is turned on

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It is an intermittent issue. I've checked mounts, fuel, plugs dont want to come out and I'm afraid to break them, coils, air filter, mass airflow sensor has been cleaned. I drove for about 20 miles on the highway and no issues. Drove into the city stopped at some lights no problem, drove some more and more lights turned on the Air Conditioner and and it shook and nearly stalled. Turned air off it was fine. Turned air back on and it shook, did this another 10 times and it shook 4 out of the ten times.

My car has 180000 miles.
My car has an automatic transmission.

A: Hey there. There is an A/C idle-up VSV (vac...

Hey there. There is an A/C idle-up VSV (vacuum switching valve) on your vehicle. The purpose of that valve is to increase engine speed at idle to accommodate the added load of the A/C compressor when the A/C switches on.

If the idle-up valve is not functioning, it is possible that this is a cause, or part cause, of the issue you are facing. In addition, of course, you could have engine tuning issues which are contributing to the rough operation and that should be evaluated as well during a tune up.

If the plugs haven’t been replaced for 100,000 miles (and perhaps less depending on age) they will have to come out and YourMechanic has the expertise to get them out safely without damage. To have this scoped out further, I recommend having a certified professional, like one from YourMechanic, diagnose the shaking symptom so that it can be properly resolved.

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