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Q: Why does my car jerk & accelerate by its self?

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My car recently started accelerating by itself when in parking gear. It doesn't do it so much in drive but when you completely turn off the ac it accelerates & de-accelerates. My car also jerks like little jerks & only sometimes, like when at stop signs.

My car has 160000 miles.
My car has an automatic transmission.

A: From what you've described, the jerking...

From what you've described, the jerking is most likely due to a misfire or a vacuum leak on the engine. You should have all the spark plugs and wires checked for misfiring after your computer is scanned for a misfire code.

You may have a leaking valve cover getting oil on the plugs and wires. Another possibility is that the engine may have a vacuum leak, causing the high idle and even the misfire if no other problems are found. A proper diagnostic should be done if any engine codes are present.

If you need help with getting this fixed, consider YourMechanic, as one of our mobile technicians can come to your home to diagnose the misfire firsthand for an accurate repair. Best of luck.

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