My check engine light came on so i went to auto zone to get the machine to check what was up with my car and is was a miss fires i changed out the gasket cover to stop the oil leaking then i changed out the spark plugs, the wire set, the cap and rotor and also the ignition coil I'm not sure what else it could be sometimes the car does take a while to turn on and my engine is shaking im not sure what it is would anyone happen to know what else it could possibly Be?