Intermittent engine shutting off

For a while, my vehicle would occasionally stop running at idle shortly after I started it up while it was warm, this was a minor irritation. Then, about 6 weeks ago, as I left work, it went about sixty feet down the road and stopped running and would not restart for about 5 minutes. But it would not idle, I could start it and rev it and it ran as long as I held the pedal down but as soon as my foot left the pedal it shut off. I took it to my mechanic, and he said it was the idle motor and changed it and I about one week of carefree driving and then it started shutting off on me occasionally at very low speeds and would not start for five minutes and then it ran well. After a few weeks of this I took it back to the same mechanic who said that it must be the fuel pump and replaced that. Well, I got another week of carefree driving until yesterday it did the same thing again to me twice. It has never done this after a cold start and has always run well, but sometimes after a warm start, it will stall out at a very low speed and not restart for 5 minutes. Any ideas would be appreciated.