Thanks to all the great reading here, I was able to finally lock down my missfire problem.

I own a 98 F150 4x4 4.6L Manual Transmission. I bought it new in 1997. It now has 222,000 miles.

At about 200,000 miles, the truck developed a slight miss under load at low RPMs(no codes were ever thrown), like turning a corner in 2nd gear and then steping on the accelerator. I had replaced the plugs with ford motocraft parts about 10,000 miles earlier, so I ruled them out. I did a little reading and figured I'd replace both coils and, voila!, problem solved...or so I thought.

Then about 6 weeks later the problem started to resurface, and was getting much worse. Now when ever the vehicle started to go up any incline or if I were to press even slightly on the accelerator, I would get a horible miss and stutter. I still figured it was ignition related so I replaced all the plug wires. That did nothing, so I thought I'd change out the fuel filter, even though it only had about 20,000 on it. That did nothing, so I thought I'd change out the fuel pump, again nothing.

needless to say by this time, I'm quite frustrated, so I started searching the forums here for answers. I started reading about similar problems others had and their own trials to fix similar stuborn misses. I think I read for about 3 hours straight and deduced that it had to be in the coils, wires, or plugs. Seeing as how I just replaced the coils and the wires, I thought I might as well change out the plugs again.(getting pretty good at it, only took 1 hr.) I decided to go back to the Autolite double platninum, as they served me well before. I changed out all the plugs and marked the old ones from which cyclinders they were removed.

Low and behold the truck was running great! I thought I'd take a look at those Motocraft plugs that I removed and when I got to #3, I saw it...a crack the full length of the insulator. I could even see the scorch marks all the way along the crack. see below...


I write this in hopes of helping some other poor guy suffering as I was.

Thanks again for all the great information located here on this forum! Now I'll see if I can get this thing to 300,000+.

Paul

 

Welcome to the forum
Glad we could help. There is tons of great info on here.
Thanks for the tip,

Jimmy

 

Started when I put in autolight plugs; ran great before the change; the old were motorcraft. I asumed I damaged the wires ; replaced them; I still have the miss. I have new Motercraft and will loock for the crack thanks. I wa ,taught in the army a long time ago not to use a plug if it were droped some inchess I forget now how many could be 12. The parts clerks throw them around. The motorcraft and the autolights look the same ;are they made by the same company?

 

Last time I heard, Autolight makes the Motorcraft plugs. They are supposedly a little different to meet Ford/Motorcraft specs.