05F150XLT

I have an on going misfire problem that's really starting to irritate me. It'll misfire starting at about 3200 RPM, and only when I give it more than half throttle. It's gone from cyl 8 (replaced ignition coil and spark plug) went away for awhile, then last weekend I was driving from Louisville to Valdosta and it was misfiring at 2-3000 RPM so I pulled off the interstate and had the codes read, it was cyl 2 so I had the ignition coil replaced. Truck ran the best it had since i bought it a month and a half ago. Now this past friday I took the muffler off, so naturally I got on it, and the same problem that I had the first time, but I don't know which cylinder. I'm thinkin maybe computer problems. Any Ideas?

Hoese

I've got the same thing going on with my 06, had it in the shop 7 times... they replaced the cats, coil packs, plugs it still misfires at random times most when it's cold. let me know if you get it fixed

snowshredder555

Do you guys get the rough running even at idle? Mine seems do be doing the same thing, it wont throw a code. Can I get the sparkplugs and coil packs at Autozone, Checkers, or Napa?
Thanks- Ted

Hoese

you can get the coil packs from any auto parts store...the plugs are $10 a piece and they have been breaking off inside the heads...do some research on that before you try changing them. i don't have much of a miss on idle, just when i'm getting into the gas around 3200 r's

snowshredder555

I've scoured the internet looking for some info and also, searched these boards as well....but the last time I was at the parts store asking about our plugs, they told me it was a dealer only item...that was some time ago though. I'll look into it..

By the way, what brand has everyone had luck with?

-Ted

ATOM

Get motorcraft plugs, i hear nothing but problems running other plugs

06KRF150

I have the same problem with mine, I have 37,000 miles and when I accelerate hard when its cold it misfires at 3200-4000 RPM. As it warms up it will go away. I just bought the truck in May and this has been happening for about 3 months now. The first time I had it at dealer for a hard starting issue also with black smoke when it started they put an injector, coil and plug in cylinder 7 that they paid for. It was fine for a few weeks then this issue started so I brought it back and they said the coils for cylinders 1,4 and 8 were bad, they refused to pay for it so I took the truck back and replaced them myself and the problem didn't change at all. I am a tech at a BMW dealer and tried diagnosing the problem myself and I can't figure it out. I put a fuel and air filter in and no change. I've been taking it back and forth to the Ford dealer next door for the past week and so far they can't figure out whats wrong with it either. Have you been able to figure out what causes this yet?

N0J0ke_FX4

motorcraft plugs are ok but the champion one peice plugs are better they dont have carbon build up on them and so they wont break off when replaceing, and also when getting coils get motorcraft all others are a waste of money

jgc2521

hey, i have the same problem 70k miles on an '06 5.4l and a p0397 code. i have new coil packs and have changed the coil and the problem still persists. I went to the dealer and they changed both cats for free under warranty, but the problem has come back. I personally think its my injector (read '05 injector problems) since i can here my cats popping from time to time. but I don't know... Have y'all found a solution?

Woody3141

if you are describing what i think you are then i had the exact same problem. (mine would misfire under load or when the engine was bogging.) The problem was better if i drove with overdrive off aswell. I was getting so mad and irritated at this problem i said something at work with all of the symptoms and randomly a co-worker of mine finished my sentence and he had the exact same problems on his 5.4 in his super duty ( i have an f150) Anyway he changed out the boots that ran from his coil packs to his plugs (new inner springs aswell) and the problem went away. I couldnt believe it would be that simple since i just went through mine because i had a coil pack go out and i changed the plugs (although i had one break-another story in itself lol) anyway, so i took all the boots off, checked them for cracks, cleaned them very well, checked all the springs inside of them, re dialectic greased them and the problem has been fixed ever since! (i didnt even have to get new boots, although you can get new boots for the coil packs for approx $10 a piece.) good luck and dont know if this is even your problem, but if its anyhelp or at least a start, good luck