Driving home from work yesterday, my car died at a stop light. No sputtering, just died as if I turned the key to the off position. It started right up without issues and got me home fine.

This morning, it wouldn't start at all. With the key in, all the appropriate dash lights come on. No CEL. Fuel pump primes and clicks off. When I turn the key the the III position, the engine cranks and fires. However, as soon as I let off the key (to the II position) the engine dies every time. While in the III position I can rev the engine so it seems to be getting fuel. I've tested all four cylinders for spark and they appear to spark. Below are the things I've replaced today.

*Fuel filter, Ignition Control Unit, Ignition Coil, Cap, Rotor, PGM-FI Main Relay

Please help!