My son a US Marine has a Ford 1997 Tarus. While driving at higway speeds back and forth on leave the car stalls out on the interstate, he pulls over and after a few minutes the car can be started again. he drives about 20 miles and again it stalls, he pulls over and in a few minutes it starts again back on the road, and constantly does this throughout his trip. What is going on here with this car?The garage says no codes are coming up and the ford dealer has taken this Marine for a few thousand dollars already. Can anyone help us fix this problem?