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Q: My car has a high idle when in park and doesn't shift properly

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When I start up my car in the morning the RPM is at 1500. It goes down when I put it into drive, but it runs really crappy. Doesn't get up to speed fast at all even when I have it floored. And it's weird when I go over speed bumps, it doesn't down shift properly. In fact, all the shifting feels pretty off. It was intermittent but now it's happening almost all the time.

My car has 115000 miles.
My car has an automatic transmission.

A: Hi there. Cold idle can be as high as 1500 ...

Hi there. Cold idle can be as high as 1500 RPM, but should lower to around 750 RPM for this vehicle once warmed up. This could be an air leak into the intake area of the engine; an auditory check for a "hissing" noise may reveal the air leak.

This could also be a sticking idle air control valve. This valve is located under the throttle body and can be prone to sticking. A good cleaning or replacement may be necessary to help this. As for the vehicle not downshifting properly when going over bumps: the transmission doesn’t downshift when going over bumps, but transmission will downshift when slowing/braking. If the transmission is not downshifting normally and the gear changes seem off, inspect the fluid for proper level and color; it should be red in color and between the hatch marks with the engine running on a level surface.

A qualified technician, such as one from YourMechanic, can assist you with an idle speed inspection and a transmission shifting inspection to make sure you get the right diagnosis and don’t have unnecessary repairs made.

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