Hi everybody, new member and first time poster.

I have a 2002 F150 5.4L, auto trans, factory tow package, 4x4, 175,000 miles. This truck seems prone to misfires- coil, wires, etc but this seems different. Driving the truck empty it has been doing well. When it was really cold this winter (single digits) it ran like crap until it warmed up- lots of bucking.

When I haul hay (1500 lbs or so) or pull my horse trailer- steel trailer w/ 3 horses on board, so it is heavy and a lot for a 150- it jerks/bucks violently off and on. Not a consistent problem but it is not nice. The tachometer is steady when these episodes occur so I think the engine is not the problem. Does this sound like a U-joint, fuel filter, or what? I would be very curious what you guys think I should look at.

Thanks!

 

I would say it is coils or plugs, if it doesnt do it when empty. The misfires are so small you dont notice them, then when you put a load on the engine, bam, there you go.