Engine Shut Off Without Warning problems of the 2009 Mercury Sable

While cruising on interstate highways, on three occasions, the engine has quit running. The first incident occurred October 12, 2012 with about 18,000 miles on odometer. The second incident occurred during may, 2014 with about 34,000 miles on odometer. The third incident occurred on April 20, 2016 with 40,665 miles on odometer. It is interesting to note that while this vehicle is used primarily for out-of-state travel, all 3 incidents have occurred while returning home from out of state trips and within about a 70 mile radius in central illinois. The engine will readily restart after a shutdown. The engine ran smoothly both before and following each shutdown, as well as all other times during the life of this vehicle. The Ford dealer checked the engine this week and found no cause for engine shutdown nor vehicle recalls. I am inclined to believe that this engine shutdown issue is not isolated to this one vehicle. I fear that such engine shutdowns will lead to a catastrophic crash particularly when the vehicle is operated on crowded interstate highways in large metropolitan areas in rush hour traffic. We travel on these highways around indianapolis, cincinnati and st. Louis. (we have already experienced an engine shutdown on another of our vehicles while traveling on a very crowded interstate during rush hour. ).