specific shake/shudder at 40-50 1100-1300 rpm
 

nuff said, only happens when there is an incline, not much of an incline is needed either. just starts to shudder i'd say. maybe even go as far as saying it feels like a jolt like trying to shift but refuses. ah i'm no mechanic so what do you all think?

you got a misfire

I had the same issue on my 99 4.2L. At about 120k miles, from 1500 to about 1600 rpms, the whole truck would get a shake and it ended up being caused by a bad coil pack.

Which engine ya got? How many miles? What's its exact ignition parts maintenance history?

5.4, 116k, um, only had the truck since end of July and haven't really had the trucked looked over yet. Only new tires.

Probably needs spark plugs and maybe cops.

alright, thanks.

Manual or automatic?

5.4 in a F-150 is only going to be an automatic.

Yep sounds like a low grade misfire. Is it happening as the truck just shifts into OD? As others have stated, most likely it's a coil over plug going bad.

Yeah probably. Honestly haven't a clue what the shifting into OD happens.

just make sure that you use MotorCraft spark plugs, other plugs wont last long and might come apart making a big mess:eek:

okay. I've already begun doing that. Going to attempt it myself. Then go somewhere if I get in over my head.