I got a 97 5.4 4x4 with 169 on the clock. I drive the truck to school and back on the interstate monday-friday total of 90 miles round trip. Made it up to school yesterday fine but on the way home the truck started to shake really really bad. Almost felt like the rear end skipping a tooth or something. It happened twice about a hour inbetween and only lasted for a few minutes then drove fine. Took it to two different shops, first said its a missfire and mechanic was able to make it (shake) by burying the gas or holding the brake and gas at the same time (under load obviously) said hes seen it before where a heater hose leaks on the coils but there is no leak. Second shop could not get the truck to act up, no codes at all, and pressure tested coolant system. Going to clean tb and air intake tomorrow just because. Plugs were replaced about 20k ago. Not sure what to do next.

 

What plugs did you use?

 

Ford plugs as far as i know

 

Drive it in the rpm/load range that you feel the shaking to try to get the computer to throw a code. If it's intermittent, you just have to play the waiting game.