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Q: My vehicle stumbles and hesitates, and the RPM go crazy

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When i first turn on the car the engine does a sort of 1-time kick not a smooth start. Also when i turn the ac on the rpm goes up about 500 and comes down, you can hear the engine rev hard. As i speed up all the way to 30 and let go of the gas to maintain that speed, the whole car does like a double shake as if it was about to go faster but does a harsh kick. And when im maintaining a constant speed of about 42 or 43 the rpm doesnt stay still, it moves up and down in 500 intervals and you can feel the engine reving without me even pressing the gas! I already changed the cam shaft position sensors and changed transmission oil even added some lucas product so the transmission wont slip!

My car has 158467 miles.
My car has an automatic transmission.

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