Q: The car will run find for about 200 miles the it will start to lose power as you are driving it but if you stop the car for about

At 140,000 miles, it really could be just about anything. It could be that there is an electrical component that takes some time to heat up and fail, but works again as soon as it cools off for a few moments. Or it could be a tank vent issue. If the fuel tank vent system is not working the car can build up a vacuum in the tank that will eventually get strong enough to where the pump will not be able to draw fuel from the tank any more. One experiment you can try is to take of off the gas cap when the car is stalled and see if there is suction at the tank. either way, you should have your car checked out. You can have that done at your convenience by contacting Your Mechanic. They can send a technician to your home or office to check out your stalling Nissan and let you know what it is going to take to fix it.