My 2000 F150 suddenly developed this rough idle situation, initially reminded me of the feeling of my Mustangs automatic transmission when it need at the 50,000km fluid service. Oh, yeah, and the S.E.L.light came on at the same time. Fortunately I was around the corner from a Ford dealer and they could squeeze me in. The diags they said would take about an hour, but it didn't take that long for them to tell me that there was a problem with the coil (at least one of them). The got me into the repair bays and out before they closed and assured me I could get home. I didn't get 20 kilometers on the truck when it started the same symptoms again. I had my son in the car and was already on the highway so I elected to make the trip an hour and a half north home. The truck seems to run o.k. until you lean on it a little bit, and the sensation gets stronger once the transmission lockups up. If I'm holding my speed It's not very apparent. If I start to climb a grade it starts to act up, until I either let off the accelerator a bit or press it down enough to kick down a gear.

This truck is a replacement for my '98 that went up in flame a month ago. We just picked the truck up this morning and now this. I'm getting the feeling I'm not supposed to own a large truck...

Any thought from the list on my mechanical problem?

 

There must have been a missfire code set for one or more cylinders.
Since you don't have that info and don't work on the truck it is hard to give any meaningful advice.
Is it the same code, the same cylinder, what did they do etc.
You seem to indicate the fault shows during cruise.
This could still be a spark plug even if a coil was changed.
Under cruise conditions the engine's spark is advanced and the fuel amount is reduced. This places a higher load on the plugs and coils. If either or both are marginal then a miss developes.
The engine's software program measures the cylinders' contribution to over all power by measuring the rotation time of each cylinder and compares it to a table.
You can see that a bad plug or anything that results in a cylinder not contributing it's normal share of power will be detected by this method.
The control systems in these trucks are very complicated for an owner to service much of the time without some basic knowledge and at least a code reader.

Good luck.