While driving from Washington to Colorado, I was driving up a long, steep hill when the car started hicuuping/misfiring. The car recovered, but then started doing it more often, even when I was driving down the hill. The tachometer would also jump around when this was happening. Eventualy the misfire was so bad, the engine stalled and gave me the "!" light. I restarted the car, but then the transmission wouldn't engage. I had to disconnect the battery to get the car to run again. Then it would run for another 60 miles before it would act up again. I was able to limp the car into the dealer in Salt Lake City. They ran a diagnostic & told me the cam position sensor was bad. So I had it replaced. Unfortunately, 300 miles later, going up another long steep hill it started happening again. I have considered a few things that could be wrong. I usually run cheaP gas & have never had a problem. Could this cause a problem at higher altitudes? I am currently driving at around 6500 ft. Any suggestions would be greatly appreciated!