Jeep runs rough when started in HOT temperatures and engine is hot.

My 1995 Grand Cherokee runs fine when it's cold, or the weather is cold. Lately, it has been near 100 degrees most of the time where I live. After driving the car someplace, if I shut it off for a few minutes and then re-start it, it will shake, rattle, and roll until I clear the engine. It's acting like a vapor lock. If I park it (when hot) and then open the hood for a few minutes, it will start and idle fine. Obviously my problem is heat related, because when I allow the heat to dissapate, the problem goes away. Today, it was around 105 degrees out and for the first time, it started doing this while it was left idleing as I loaded items in the back. It started shaking, and then blowing a large amount of blue smoke. After getting in it and driving it for a few blocks, the problem cleared itself and all was fine. This doesn't seem to happen on days when the temperature is below about 75 degrees. Any ideas?