'99 expedition 50mph hesitation

[geoff]

At start the truck runs sort of rough but then driving is fine until you hit 50 mph then it almost feels like it's going to stall and then at 55mph it takes off running fine again. It sometimes does it when you try to accelerate hard too, when passing on the freeway.

This was happening about 1 year ago and I changed out the spark plugs and the fuel filter and it ran better but now it's doing it again.

Maybe change the wires? Throttle sensor? Coil on plug??

Help,
Geoff

[Bill65]

I had the same problem. couldnt find the problem, finally got a check engine light for a misfire. switched the coil to another plug and that cylinder misfired. I put a new coil on and it has been fine. not sure how to test them.