Hi guys 02 screw 5.4. Ok so when my truck is at idle after warming up it shudders every now and then. I look at the rpms and they aren't dancing aroun. Also when I hit about 35 there is a strange vibration in the floor like its coming from the whel. But it's goes away after that. Any ideas or am I just paranoid.

 

It sounds like you might have a coil pack problem, probably allowing it to short to the engine. When it throws a code, you can find out which one it is!