If you have a Zetec, check the wireing to the crank sensor. Make sure it is not to close the the header. If it is, the wires can melt allowing the + and - wires to come in contact with each other. This can be intermittent and cause sputtering or engine ceasation. It can also correct itself when the engine cools. A real PIA to diagnose and find. Or, it can be constant causing the engine to stop and not restart. We replaced my wireing and wrapped it in heat shield and also made a heat shield to cover the crank sensor. Problem solved.