I have replaced PCM and the Crankshaft position sensor and all 8 coil on plugs and it still runs very ruff.
What else is there in the ignition system of a 98 Mercury Grand Marquise 4.6L GS?
PCM replaced, Position sensor replaced, COP replaced.
November, 15, 2012 AT 4:55 PM
It don't have one, it uses cam and crank sensors to tell the PCM that the engine is turning over and then that starts the firing order sequence by firing the injectors at the proper time. You didn't mention anything about replacing spark plugs and if so what brand and type did you use? It may be a bad injector.