P0300 random misfire

Question

I have done a tune up, changed plugs ,wires,coils, even cleaned the throttle body and checked the fuel injectors. Changed the egr valve. Checked for vacuum off of the secondary air injector. I was always told to start from the top down. So would it be the catylitic converter? Could the catylitic converter be the problem or is it a electrical problem? My 1 and 4 plugs are black but my 2 and 3 plugs are fine. Where do I look at to find the problem? Oh and I'm finding oil around the plugs.

Answer 1

Possible that would be the catalytic convertor, When it comes to a misfire on Saturn , the ignition system is where the misfire is mostly suspected for the misfire condition. If it is a catalytic convertor related being plugged up you would be able to hear a airflow coming out of airfilter housing, not only that the intake air temperature would be closer than 10 percent of the engine coolant temperature.