Hey guys i am having annnn issue with the p0300 multiple cylinder misfire. this is a weird one i must say. but normally my car runs just fine all day long, no misifring or anything. except when i go take it to the fleet farm touchless car wash. i pull in with it running normal but shortly after the pressure sprayer starts blasting at my car. its starts to idle rough and i can feel the engine start stumbling/studdering. after the wash is done & i put in drive & begin to start driving and its stumbles bad and my check engine lights come on and flashes on and off. i check the code and get p0300 random cylinder misfire. this only happens when i take it to the car wash. if i leave the car sit for like 15 - 20 mins then i can go get back in it and it ruins normal again. im puzzled with this issue.
if it helps any i just had the shop replace my cats on the drivers side not to long ago.
like i said this only happens after going through the car wash
if it only misfires when you go through a car wash, your ignition system is getting wet and arcing somewhere.
with the engine running, spray salty water on your coil pack, and all your sparkplug wires all the way from the coil to the plug, look and listen for any arcing.
if you find a connection is arcing, try applying some dielectric grease to it and making sure the boot is tight/secure.
if you find a wire is damaged and arcing, replace it. or preferrably all of them.
+1 232, you can also just check it at night in total darkness with your car running. We do it in an enclosed garage with a vent tube for the exhaust-going outside of course......
+1 232, you can also just check it at night in total darkness with your car running. We do it in an enclosed garage with a vent tube for the exhaust-going outside of course......
well, he says unless it gets wet it will always run fine, so unless he sprays it i dont think he will get it to arc. but it will still help to do it at night since arcing will be much more visible.
oh and if you do it in a garage yes you absolutely want to vent the exhaust outside...i remember a new tech at work once tried to do an induction (seafoam) a car in the shop without venting the exhaust...lol needless to say he pissed off quite a few people that day.
sorry i havent gotten back to you all until now but ive ben busy like crazy.. havent gotten around to trying out your sugesstions yet but i will try that today or tonight and see if there might be arcing some where... and also i do have a CAI installed but im pretty sure no water is able to get inside through the CAI but ill double check that also. i will post my results later on tonight to let you guys know whats up thanks for your help any other suggestions in the meantime would be great thanks
Well i was able to get time to check out the problem and sure enough it was my plugs wires archin out in a few places so i installed a set of factiry wires on there and everything seems to be fine now! thanks very much for all the help once again you guys rock thanks again
Well i was able to get time to check out the problem and sure enough it was my plugs wires archin out in a few places so i installed a set of factiry wires on there and everything seems to be fine now! thanks very much for all the help once again you guys rock thanks again
2001 V6 Mustang multiple misifire issue 
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