P0300 Misc misfire - rough idle - bogging
Thread Starter
Heel & Toe
Joined: Sep 2011
Posts: 18
Likes: 0
From: Providence Forge, VA
P0300 Misc misfire - rough idle - bogging
Received this code back in June. It went away and came back. I reset it and has NOT come back. I did add a can of fuel line cleaner. Now, it seems to idle mildly rough, almost unnoticeable and occasionally will bog down after running 70 mph for a couple hours. It only lasts about 5 seconds and returns to normal.. any suggestions? Mass air flow? Gas filter? ( I hope not). Thanks in advance.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,631
Likes: 4,076
From: Cape Coral, Florida
Can be just about anything so instead of wasting your time and money find an automotive diagnostician (not mechanic) who will diagnose it quickly and accurately with the right equipment.
Melting Slicks
Joined: Feb 2018
Posts: 2,184
Likes: 1,050
From: North Texas
If you don't have the proper test equipment, you're just firing the parts cannon at your problem.
If you lack the equipment and knowledge, then find a professional automotive diagnostician.
I give a dealership a 20% chance of fixing it the first time with replacing only the part that is causing your problem.
If you lack the equipment and knowledge, then find a professional automotive diagnostician.
I give a dealership a 20% chance of fixing it the first time with replacing only the part that is causing your problem.
Racer
Joined: Jul 2015
Posts: 405
Likes: 99
From: Chicago IL
St. Jude Donor '16
Misc misfires
Received this code back in June. It went away and came back. I reset it and has NOT come back. I did add a can of fuel line cleaner. Now, it seems to idle mildly rough, almost unnoticeable and occasionally will bog down after running 70 mph for a couple hours. It only lasts about 5 seconds and returns to normal.. any suggestions? Mass air flow? Gas filter? ( I hope not). Thanks in advance.
I suggest locating some with a more sophisticated OBD2 scan tool. They’ll be able to pull the misfire history. Cylinders 1,4,6,7 are your DOD/AFM cylinders. If it’s one or more of those cylinders consistently misfiring, it’s most likely a stuck lifter. If it’s any of the other cylinders, it could be a spark plug, spark plug wire, injector or ignition coil.
Please let us know what you find.
