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Q: Random misfires

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About a month ago, I started getting misfires at random times. Since then, it has gotten worse. When the car starts up like normal, every three seconds, it will misfire, and the catalytic converter gets hot - hot enough to turn red. The code reader just gives me "P0300" - random misfire. I have checked the coils, and they were fine. We switched them out anyway, and that didn't help. We tried using three ignition control modules, but there was no change. A new ignition coil went in yesterday, because the old one had a slight burn mark and was arcing. When I changed it, the car ran fine for a second, then went back to misfiring. There is a lot of clear condensation coming from the exhaust, but I don't think it is anything bad like coolant or oil. What could be causing these misfires?

Hello. There are several possibilities that could explain why you are having this problem.

  • One possibility is that you could have one or more faulty fuel injectors, or the fuel injector wiring is damaged.

  • Another possibility is that one or more spark plugs have fouled out.

  • It is also possible that there are bad internal engine parts.

I would suggest that you have a certified technician, like one from YourMechanic, come out and diagnose your car to find out why your engine is misfiring.

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