I am having trouble with my sons 94 f150 5.0 the motor is very rough running at highway speeds in the 40 to 55 miles ph if you punch it it smoothes out or let off the gas it smoothes out even siting in the driveway I can just barely give it a little gas and you can see the engine start to shake at a certain point then it will smooth out if you give it a little more gas.

Have tried changing the plugs and plug wires ran a can of lucas cleaner through the tank but still doing any ideas would be greatly appreatied

 

i woulda guessed wires and plugs did you tune up ignition?

a guy came in with the same problem 2 days ago (he had a mustangs though)
and it turned out to be his EGR vavle so mabey check that??


but good luck

 

wouldn't the egr valve show a code ?? I have no codes showing up.

 

May seem too simple, but my truck does that exact same thing if it's rained a lot and the humidity is very high. Seems between 1500-2000 RPM it kinda bucks and hesitates, above or below it's fine. For me the problem goes away after 20-30 minutes of driving, I assume when engine heat dries everything out. Sometimes it trips the check engine light(goes off in a few minutes), sometimes not.

 

Follow this exactly: