Re: 1997 Ford F-250 5.4L V8 Triton
I'm running into the same problem with my Ford E350 van. It started as a gradual skip, and progressively got worse. I bought a cheap code reader, and it was telling me cylinder #5 was misfiring. I'd erase the computer, and a short time later Cylinder 5 would misfire again, and on a rare occasionally 4 and 8.
I replace the coil on Cyl 5 and there was a huge improvement. However I still get a major shudder at low RPM's as soon at 45-50 miles per hour. I notice it particularly on a slight uphill section of highway around 50 mph.
I cleared the computer and checked again for misfires, but there have been NO misfires. The shudder is very noticable, and I'm down to three suspects.
My primary suspect is the mass air flow sensor, or what ever the sensor is that is located in the round air cleaner case. I was handling the unit while the car was running after replacing the coil and the engine rpm started going up and down while idleing. It continued to go up and down, and then finally cleared up after about 5 minutes. I'm thinking a case of air fuel mixture being too lean causing a buck at low rpm, high speed. This would also be supported by the fact the outside cylinders were reporting misfires, with the exception of cyl 1 (4 -back right, 5 front left, 8 back left)
My other suspect is the EGR which kicks in at highway speed. It could also cause something like this, but I'm not getting any engine light or diagnosis codes.
My third suspect is the transmission lockup torque convertor turning on and off at that speed.
One final clue, if anyone can help, is the van accelerates fine at wide open throttle all the way from zero to 70mph. No issues, it's only at about 20% throttle I see the problem.
Also I"m confused by Gary's statement to replace all 8 coils??? Sure it would work, but replacing the entire motor might fix it too. I would expect to see the computer show me a skip if there was a continued misfire.