Hey everyone, I'm hoping someone can help me out. I have a 1997 Ford F-150 XLT 4.6L 4x4 Auto and it's having an issue. My truck has recently developed a stutter when accelerating. It feels like a serious misfire and actually pulled a code for a misfire on cylinder 7 (although I haven't been able to get the code to appear again). The plugs are pretty new, I think I only have around 10k miles on them so i figured it might be the coil pack. I bought 2 new coil packs but only one was in stock so i replaced it on the drivers side bank (which controls cylinder 7) and it didn't fix my problem. When I first start the truck and drive it, it isn't very noticeable, but as I drive the truck for a few minutes, the stutter gets more violent. I will replace the other coil pack tomorrow, but I have my doubts it's the problem. Anyone else have any ideas? It acts just like a bad coil pack. Any help would be great, Thanks!

- Mike

 

15 YO motors can have a lot of miles on them. First thing I'd suspect would be spark plug wires. Especially IF only "plugs are pretty new".

Any idea how old/how many miles are on them?

 

Don't rule out one of your new spark plugs may have failed.

 

Plug wires are probably original to the truck. The truck has 130k miles on it. I wouldn't think it would be the plugs, I put the motocraft platinums in it. They are nice plugs, plus it's spastic. I would think that it would be a totally dead cylinder if the plug went bad. I've never really heard of a plug only working some of the time.

 

Anyone think it might be a camshaft positioning sensor?

 

I doubt it. I would take a good look at wires, especially #7 since that tripped a CEL. That sits almost right below the DS squirter. Did you check for moisture in that hole?

 

I am having a similar or I should say exactly the same problem but it has never thrown a code. Put new plugs in in july. Mine has COP's so there are no plug wires. just a plug and connector with the 2 small wires diving into a wire harness. This problem is driving me crazy as well. Mine usually happens in between 1200 and 1500 rpms but if I step on it it takes off like a rocket. Are there 2 fuel pumps , A low pressure and a high pressure or am I heading in the wrong direction all together. I have a '99 5.4 ltr. and am going to change the plugs and try to test each cop while thier off. The last time this happened (in July) changing the plugs fixed it so it's worth another shot.

 

No I have not yet checked it for moisture, but i used plenty of dielectric grease when I put the new plugs in so I don't think that would be the issue (although i'll double check tomorrow). I runs fine when I first start it and gets worse as it warms up, which makes me think its a camshaft positioning sensor. The sensors are only about $20 so I think I'll try it first. If that doesn't work then I think wires will be the next thing I try.

 

I just thought that I would let everyone know what the problem was. Turns out that I was right to think it was the cam positioning sensor. I replaced it and the truck returned back to normal. My old sensor had a bunch of crud/sludge on it (I'm religious about oil changes so the sludge makes me wonder about the POs habits).
I even took the truck out and played around in some of the snow today

 

That's good to know. Not a common item to go bad.