Engine stalls

Awesome site. I have a Mercury Grand Marquis 97 with 99,000 miles on the 4.6 L V-8.
Engine stalls after driving in the heat for 15 mins or more. Will start right back up again. Is more likely to stall when A.C. Is on. A.C. Compressor will cut out and air gets warm. About the same time engine will stall. Usually happens when driving very slow in a parking lot, but the longer I drive it the higher speeds in will stall at. :( Engine temperation is in the normal range. Today when this happened the A.C. Cut out, the engine stalled and we then had problems with the right front electric window working with switch on passenger door. Had to roll down with driver door switch.