Cadillac DeVille 1985 to 2005 including:1985-1992
Throws code P0300 (generic I know)
Replaced coils, plugs, both upstream 02 sensors, idle air control valve, throttle position sensor, valve cover gaskets
Car was running great. Went inside store, came out and cranked car. Immediately started rattling. Could hear severe misfire. Lost brake...