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Q: Engine idles rough and jumps between 500 and 1200RPM when shift from Drive to Reverse; Check engine light on

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The engine seems fine most of the time but it idles rough and occasionally jumps between 500 and 1200 rpm when I shift to drive or reverse. When I throttle and it hits 4000 rpm, the 'Check Engine Light' starts flashing. Can you give me advice as to what to do to fix all of this?

A: You may have a couple of separate issues: ...

You may have a couple of separate issues:

  • The flashing Check Engine Light under heavy load is most likely an ignition system misfire. This could be something like a coil pack or worn spark plugs. These engines are known for going through coil packs so that would be my first guess.

  • The rough idle could be related, but it sounds more like a vacuum leak or possibly a faulty idle air control valve (IAC).

The first step is to retrieve the diagnostic trouble codes for your Check Engine Light which serve as a starting point for any further diagnosis. I suggest you have a trained professional, such as one from YourMechanic, diagnose your vehicle firsthand.

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