I need some help in a matter that no one can figure out. I have a 2001 3.0 Automatic 2wd. It has 105,000 miles on it. It runs well until I drive it a long distance like several hours on I-95 a while. All of a sudden it starts this hard miss or clunk. It does it frequently and it almost feels like something is trying to lock up. It never does it around town or driving back and forth to work. I just changed the plugs and wires about 6 mos ago. Help?