Engine Performance problem
2000 Ford Ranger 6 cyl Two Wheel Drive Automatic 64,000 miles
----------------------------------------------------------------
My Ranger has been missing/ almost lurching on slight grades at freeway speeds. This is not a constant thing but has come and gone. I have been using premium fuel with an injector cleaner added and thought that had done the trick. However today with a load and on slight grades the missing occured.Any ideas would be a help. Thank you.

tune up. replace plugs and wires.