1999 Pontiac Grand Am Engine cranks but wont start or stay

When I went to start my car this morning the engine cranked but wouldnt start. After several attempts I palyed with the accelerator and it started but as soon as I released the accelerator pedal the engine turned off. I made several more attempts and even got the engine to operating temperature but the engine would always turn off after releasing the accelerator.
I was experiencing this same problem when I posted my original question (12/26/09). I replaced the IAC valve as suggested and the engine ran fine until this morning. The plugs and wires are less than 6 months old. The battery is about 1 moth old. There are no trouble codes present. The fuel and air filters were just replaced. The fuel presssure was checked on one of my many trips to the mechanic for the first problem and I was told it was OK (55psi).