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Got a 99 chevy s10 with a po 303 code any help would help

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Your P0303 means: "Cylinder #3 Misfire Detected." This could involve a simple matter of a bad spark plug, plug wire or something a bit more serious. If you have separate coils for each cylinder or groups of cylinders, then you need to check the coil pack to the coil over #3 Cylinder. Sometimes it could also mean a vacuum leak ANYWHERE on the Engine and lastly a Valve problem in that the intake or exhaust valve on Cylinder #3 is carboned up. I would recommend getting a Haynes Manual, available at most part stores to go through their diagnostic as to your misfire. Remember, in obtaining a Code, it has a lot more to do with a simple 'misfire detected', it's a starting point to where to look. A vacuum gauge and a compression gauge would help should it not be something so simple as a spark plug, plug wire, coil or a distributor cap & rotor button that has too much corrosion on it.

I hope this helps you a little,

As Always,

"00 Buck"

Posted on Jul 18, 2010


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