basster

replaced wiring, plugs, fuel filter and my check engine light turned off and ran fine for about 4-5 months...Now it's running tough and hesitates when I accelerate hard, going up ramps, going at higher speeds and when at idle. Seemed to work a little better when I take the overdrive off but I know it's not the tranny since it still misfires when at idle. Any suggestions, I've got a 97 f150 w/ 4.6V8...155,000 miles. THANKS!!

zutmeloda

look at the o2 sensors they may need to be replaced or cleaned

DaleD

Just went through all that at the same mileage. I replaced the coils, plug wires "earlier", and the plugs. Went to auto zone when my light would come on, 5 times same reading, sparkplug number 5 misfire it would read. After finally giving in, I replaced the plug wires again. Turned out the Motorcraft Wires that number 5 was bad from the begining and just keep getting worse. Everyday the engine would run different. Mine is a 97 4.6 with 153,000 on it. And it's a pleasure again to drive down the road without a stumble or a missfire at idle. Auto Zone loves to put the scanner on your car for free. If you got one in your area, take it in to them.

Dale