Random misfiring

toyota
corolla

#1

i have a problem that has been going on for about a year now at 188000 miles i had a code po302 to fix it i had replaced the distributor, cap, plugs, wires still had the problem went to the dealer had fuel pump replaced gas tank dropped gas lines cleaned car runs a lot better but still misfires at times does not matter if hot or cold does misfire a bit more when on the highway does not matter if accelerating or coasting i now have 198000 miles on it not sure what else to try before the major tune up the engine was running perfectly


#2

Before what major tune up the engine was running perfectly? Do you mean after the distributor, cap, etc.? If so, a car throwing a misfire code is not running perfectly.

In the midst of all of this has anyone checked the compression. If the answer is yes, try to report the actual numbers - don’t just say “it was fine.”

If there still a code associated with this misfire? Is it still P0302?


#3

i only had the p0302 code before the distributor and major tune up work work was done since the work was done i have not had the engine light come on even though it still misfires at times since the repairs i had changed the spark plugs again and use fuel injector and fuel system cleaner at least 3 times. Yesterday was the first time i drove the car with no misfiring whatsoever it happens totally at random i can not see any type of pattern i don’t know if the computer will still generate a code even though the check engine light is not coming on.


#4

You need to check the compression. If that’s good then I’d next look at the #2 injector. You can swap it with another to see if the misfire moves with the injector.


#5

if it does seem to be an injector i imagine i should replace them all shouldn’t i ??? i had replaced them once at 104000 miles i have driven about 94000 miles since they were replaced or should i first try having the injectors professionally cleaned when i had the fuel system work done i was told that i had some diesel fuel mixed with gasoline


#6

What you do in terms of injectors is up to you. Personally, if I found an issue with one I’d replace them all - or there are companies that recondition then. I have no experience with that b/c I have never had it done. I just know that those companies exist.

Of course, at this mileage sometimes you just want to keep the costs to a minimum. If you have access to a scantool its not that hard to do a basic injector balance test. Or you could ask a shop to do one. If you find 1 bad injector but 3 that behave about the same then you might think about just replacing that one. Some of that would have to do with how hard it is to pull the fuel rail. On this car its probably not a major ordeal.