Manager Forum

I HAVE A 02 F150 5.4 CYL. 4 MISFIRE. HAVE REPLACED ALL SPARK PLUG AND COILS. COMPRESSION IS GOOD. I HAVE ALSO SWAPPED THE INJECTOR AROUND AND NO CHANGE. MISFIRE IS REAL INTERMITTENT BUT REAL BAD AT HIGHWAY SPEED REAL LITE THROTTLE.

ANY IDEAS AND HELP WOULD BE APPRECIATED THANKS

Any codes stored???? Can you see mode 6 data for misfires w/ your scan tool??? Are you sure it's not TCC shudder in the torque converter???


Jeremy

YES. P0304 CYL. 4 MISFIRE. DON'T HAVE ANY SCAN TOOL WITH MODE 6. IT WOULD BE AWESOME. THE FAULT ONLY RETURNS AFTER DRIVING DOWN THE HIGHWAY, BUT YOU CAN FEEL IT AT IDLE BUT DOESN'T HAPPEN ENOUGH TO THROW LIGHT. SOME DAYS IT TAKES MANY MILES BEFORE IT THROWS THE LIGHT.

Maybe a sticking valve after the motor comes up to temp???? Try using a good motor flush and oil change & or fuel inj service to de-carbonize valve stem???? Just some thoughts

Jeremy

i believe those had an issue with the egr runner in the intake. i've pulled a few and cleaned them.

agree about the egr valve. I have also seen wiring issues on the coil circuits. Tough to sort out but fun. I had one some time back where the cam sensor was funky and created misfire on only one cylinder. Lab scope picked that one out.

You could unhook the EGR and drive it and see if the misfire goes away, if it does you know you have a problem in the EGR passages, some cylinders could be getting more EGR then others and that would cause a miss.