Car sputers when temp. is hot


I have a 1992 Buick LeSabre with over 193,000 miles on it. It runs fine 90% of the time but those few days a year when it gets 85 degrees or higher it will start to sputter and lose power eventually shutting down. If I shut the car off for anywhere from 5 to 20 minutes it will start up and run fine for the rest of the day. I gave the care a tune up and changed the tranny fluid and filter. If you have any ideas please let me know. Thank you.