I have a 2002 F350 Super Duty with the 7.3 and a measly 114K miles. At low speeds (10-20 mph) it pulses like I was gently pumping the gas. The RPM's don't seem to change but the pulsation is noticeable. At highway speeds or under load it runs like a champ. Maybe it just doesn't like going slow? Any ideas?

 

Does it seem like it's romping? have an extended 'romp' cold at idle as well? ...Romp, Romp, Romp......

 

I guess you could call it romping butit runs smooth when cold. This actually seems to be more apparent when its been run for a while. It reminds me of when I was young and tried to trick my girl into thinking I was running out of gas, but not as severe. Fuel filter possibly? Also, no Check Engine light so thats good I hope.

 

Change your H2O/ Fuel separator, drain andcleaning of the tanks maybe necessary,and try running TRUCK STOP diesel fuel (constant fuel turn-a-round, less contaminants, less water).