My Grand Marquis with over 205,000 miles runs and drives great. I just took a long trip to Washington DC and climbing the mountains made the temperature go up which I have never seen but I also have never climbed those big steep hills. Car eventually started not maintaining speed to the point of getting down to 25 mph in a few steep climbs. Felt really like it was being restricted and would also feel like a misfire. Once back on flat ground car was driving fine after a short while. My gut feeling is telling me the transmission fluid may be foaming or losing viscosity causing the transmission to act up feeling like a misfire. Any thoughts are appreciated as I have to go back home that way over the mountains. I was pushing the car pretty hard doing 85 + mph up the hills which probably didn't help and maybe I can be more gentle to baby it home. Maybe I should visit a quick change and have the fluid changed before going home. Again this is a guess as did a partial fluid change a few years ago. It looks red and doesn't smell or look dark.