I have a 2000 mustang gt that has 93k miles. It is throwing a p0303 misfire code. The engine is running rough, but only when it is cold. I can only notice the misfire and rough running when it is at idle and cold. After it is warmed up to operating temps, it runs great. Items I have tried so far:
Thanks all!
- All new plugs installed(Motorcraft plugs). no fix
- Moved cyl 3 cop to position 1, still threw cyl 3 code (has aftermarket accell COP's on it)
- Moved cyl 3 injector to position 1, threw cyl 3 code still
- cleaned all connectors under the hood that i could get to with contact cleaner(including the COP and injector connectors)
- checked wire bundles, found a wire bundle that had the insulation worn off but no bare wires showing, repaired it, no fix
- cleaned MAF sensor and intake duct cleaned (also has aftermarket air intake, greenfilter)
- replaced Intake air control valve no fix
- tried different octanes, 93 and 87, i know its supposed to have 87 octane per the manual, but just to try something i put a tank of 93
- Ran injector cleaner through the tank
- Ran load test on alternator and seems to be fine (stays above 13v when loaded and lights dont flicker or anything to indicate a bad diode)
- Just a note: they replaced the battery just before I purchased the car(have had the car for about 2 months)
Thanks all!
Last edited: