I have a check engine light and a generic 0304 #4 cylinder misfire. I have replaced the plugs, wires and now coil pack but the light reappears. I am a good mechanic but on construction equipment. What would be my next move? Fuel injector?
Misfires are usually caused by one of 3 things:
- poor/no spark: you've addressed most of this with spark plugs and cables. Grab a timing light and make sure you are getting steady evenly spaced spark on each cylinder.
- no/not enough fuel: test your fuel injectors with a multimeter and measure your fuel pressure too.
- low/no compression: do a compression test on all 4 cylinders, make sure they are even and close to spec.