Sounds to me like a bad spark plug insulator, which is shorting the electicity from that plug to the head and thus not firing the cylinder.

30 seconds on a scope will tell what is happening. Take it to a shop, and have them put the car on a scope, and you will see the electrical characteristics (or lack thereof) for each cylinder on the screen. A good tech will diagnose the problem just from that.

You can get new insulators for around $25-30 each, or better yet probably best to just get a new set of plug wires.

Good luck.

CHeers,
Gerry