two words: BAD GAS!
(not that kind!)
Seriously, its very possible that bad gas is the culprit. I had the same problem 2 years ago. Apparently, these cars can't handle bad gas. Try adding gasline antifreeze or octane boost to the tank, add premium fuel(from another, reputable gas station!), and beat the crap out of the car for about 20 minutes(I meant hard driving, not with a hammer! :p ).
You will probably have to keep your foot on the gas while driving to the gas station to keep it running, but it'll be worth it if that's the problem.
That worked for me...
