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Q: Car accelerating while in park, shifts slowly.

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My car takes too long to shift gears. When in park, the car accelerates by itself.

The most likely issue here would be a faulty idle air control valve. This can cause the RPMs to rise when the transmission is in park and the engine is just idling. When the engine is not running correctly, the transmission will act differently than it normally would as well. This is sort of a cause and effect deal. I would recommend having your IAC inspected by a professional to determine if it is faulty. If so, have it replaced and see if your transmission reacts differently. If not, check the fluid level. If the fluid level is low, the transmission will also react differently.

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