My 01 4.0 has a problem maintaining even speeds in cruise. It varies back and forth 3-5 mph. My 95 held cruise speed great. Could this be a mechanical issue or a model year problem? ie crummy cruise in the later years

 

Is this on flat terrain or pulling a hill? Flat it shouldn't do it, on hills it's common. You may have a small vacuum leak due to a line or cracked tank.

 

Like Big David said, Start by checking for any kind of vacuum leak. A small leak could cause it to fluctuate.

 

Flat terrain is the problem. Hills I would expect it to happen. I'll start looking for a vac leak. Thanks!