My daughter's escort will sometimes idle rough, to the point where it will cut off. During that same time it will also idle correctly. THe RPM's will drop way down and then they will pick back up again. When we are driving the same thing will happen, the RPM's will kick down and the car will become super sluggish and will want to cut off.
Rough idle. on 1999 Ford Escort
It's possible that the fuel filter is clogged and needs replacement. If the filter hasn't been replaced in recent memory then it's probably time anyway. I'd use a fuel pressure test gauge and check the fuel pressure while it's running and on the road. If the fuel pressure drops and the engine loses power then I'd suspect the fuel pump of you know that the filter's OK.