Hey guys it's ben awhile.my question,I have a 2002 chevy trailblazer and it spit out a po303 code #3 cylinder misfire, this truck don't have spark plug wires but it has a coil for each plug.what may cause this . Thanks

I would replace the spark plugs first (ACDelco only). If problem persists, replace #3 coil on plug (COP). Disconnect negative battery cable, before beginning work.

Good job. COP failure is common. As an aside, I believe worn plugs, with excessive electrode gap, contributes to COP failure.