Thread: Random Misfiring P0300 Code

Car started having a rough idle last week and developed into a miss. Ran kinda weird and was missing pretty bad at idle but still drove fine. Two days later finally set a service engine soon light and I had the code pulled. P0300 Random Misfire... which pointed me in no direction at all.

So I already replaced the plugs and wires about 5000 miles ago along with a new MAF sensor. I've ran fuel injector cleaners through it.. octane boosters... and disconnected the battery for a few a few hours and plugged it back in. Still same issue. A lot of threads on here don't have solutions just the problem so its hard to research on forums. But I did find a lot of people saying could be a clogged catalytic converter.. so I loosened up the crossover pipe to allow the exhaust to leak out before the converter and it still misfired. Running out of ideas and dont have much money at the moment. I also pulled the plugs today and they all looked perfectly fine.. dont have a gapping tool but I set them all when I put them in. Ideas, comments, or suggestions?

Originally Posted by spcguy88

Car started having a rough idle last week and developed into a miss. Ran kinda weird and was missing pretty bad at idle but still drove fine. Two days later finally set a service engine soon light and I had the code pulled. P0300 Random Misfire... which pointed me in no direction at all.

So I already replaced the plugs and wires about 5000 miles ago along with a new MAF sensor. I've ran fuel injector cleaners through it.. octane boosters... and disconnected the battery for a few a few hours and plugged it back in. Still same issue. A lot of threads on here don't have solutions just the problem so its hard to research on forums. But I did find a lot of people saying could be a clogged catalytic converter.. so I loosened up the crossover pipe to allow the exhaust to leak out before the converter and it still misfired. Running out of ideas and dont have much money at the moment. I also pulled the plugs today and they all looked perfectly fine.. dont have a gapping tool but I set them all when I put them in. Ideas, comments, or suggestions?

I would check the coils next. Maybe even the ICM.

i agree with bedwards. check the coils. get some good thick rubber cloves and pull a coil wire loose and see if ones not firing.

also if its not a coil. check the oil and see if u have water mixing in the oil. when i bought my car it had a p0300 code and water in the oil. the lower intake gasket was blown bad causing a coolant leak and missfire. also check the fuel filter.

Originally Posted by 99GPGTP

i agree with bedwards. check the coils. get some good thick rubber cloves and pull a coil wire loose and see if ones not firing..

Yeah I did that minus the gloves.. cyl 6 is definitely firing.

I do have a coolant leak.. its not that bad though, at least not on the outside.

Yeah, it was leaking externally for a while pooling underneath the supercharger and recently it doesnt seem to be leaking much anymore.