Since our weather has turned cold with lows just above 0ºF and highs around 10ºF, and we’ve had 9" of snow this week, I have been driving a seldom used 1994 LeSabre rather than my “nice” car, an '08 Grand Marquis. There’s no point in exposing the newer car to salt and slick streets. At least the interstates are completely cleared off. The LeSabre runs great despite its 177K miles. The only issue I have with the Buick is that it has died repeatedly after a 20 mile run up or down the interstate. I lift my foot or tap the brake pedal to turn off the cruise control, and the engine dies. The first time it did it, I pulled over, stopped, put it in park and restarted it. Now that I know what it’s doing, I keep rolling, put it in neutral, and restart it before getting to the bottom of the ramp. I does it ALMOST every time after a long 65 to 70 MPH run. It was not doing it the last time I drove it at more bearable temperatures, in the 40s or 50s so it may not be a problem next week. It does not seem to do it going from stop light to stop light, even at low temperatures. It has the 3.8 Liter V-6.
Any ideas why it might be doing this?