We have a big mystery issue with our 98 Nissan Pathfinder. About a year ago it started to buck and jump like it was missing gears. This happens only after driving it at high speeds for about 45 minutes. The car revs and the RPMs shoot up, the car won’t accelerate, and the car lurches when pushing on gas pedal as though it were jumping out of gear and slowing down. It goes in and out and it is hard to keep the car at speed for highway. Mechanics have said it is not the transmission, not the ignition coil, and no other problems show up.