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Q: Trying to fix a P0302 code

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Check engine light came on, car has rough idle when in gear only and smooths out when accelerating and when in neutral and park. I put in new plug, plug wires, #2 cyl coil pack. I have a fuel filter to put in next. Any other suggestions?
My car has an automatic transmission.

P0300 codes are misfire codes. The last digit indicates the cylinder where the misfire has been detected. So your work on the 2nd cylinder ignition is on the right track. But when you have a car that misses at idle but not under load as in accelerating, you might have an air leak. If air is getting into the Number 2 cylinder through a broken fitting or a bad intake gasket, it will dilute the fuel mixture and cause a misfire. Check carefully for bad vacuum lines or small plastic fittings that are broken off. Inspect the joint where the intake manifold connects to the cylinder head. Any fault in these areas can lead to a misfire at idle. If you want to bring in some professional help, contact Your Mechanic. They will send a technician to your home or office to diagnose your misfire and tell you what can be done about it.

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