Mechanics please help

I have a 92 Mitsubishi diamante that runs great.........BUT!!! When it's hot outside it dosn't want to start and when it does it quickly dies. I hit the key and it starts up again but than quickly dies again.

This only happens when it's hot outside wether the car is cold or has been driven. I assume this is some kind of Sensor malfuction but I'm guessing. Like I said it runs great when it's cool out, fires right up and purrs smoothly.

Anyone have any Ideas???????Thanx in advance