I have an automatic '99 Chevy Cavalier.
It runs great, but I've noticed it shuts off on me when it's hot outside, it runs well during the Winter months. I don't know if it overheats or not because everything seems fine; There are no leaks, coolant is 50/50 and on level and the temperature gauge needle doesn't go in the red zone.
The first thing that happens is that when I step on the gas while driving, it takes a little bit longer than usual to respond, then when the car is idle and I press on the gas my engine lights come on and then everything shuts off.
This is very dangerous because it almost died on me while turning on a big intersection.
I've heard a million posibilities: Adjust idle, Thermostat, Vacuum leak, Vapor lock, Wrong oil etc...
What do you think it is? Help please...

As simple as it may sound, the fuel filter could be the culprit. That's what happened to me - and my filter was only 10,000mi old. I had the same symptoms - slight hesitation when accelerating, but when I went to accelerate from a stop at times the car would simply die. I could restart it, but whenever I tried to give it gas, the thing would die.

I tried nearly everything to fix it. Turned out to be the stupid filter and I only replaced it because I was testing the fuel pressure at the filter fitting and figured I might as well replace the thing it if I had it apart.

Hopefully that helps.

I suggest just change the fuel filter too. Easy problem solved if that's it. Simple think to restrict the fuel flow if its clogged.