Bad Stumbling Problem
 

Suddenly today the car started running VERY poorly. I made it up all the hills necessary to get home, but the engine stumbles badly. Occasionally backfires. The stumbling did not seem to be associated with high or low speeds, open or closed throttle, high or low rpms. Just a constant stumbing. I'm going out to investigate. I'll look at ignition quickly, then perhaps see if the fuel pump is delivering enough volume. But, that's the crazy thing. It feels like it's having a fuel delivery problem but it runs just as poorly at low speeds as at high speeds. Idle seems normal.

Plug wire fall off? Backfiring usually signals ignition problems.

Bingo, Jeff. Apparently these engines run best when all the ignition wires are physically connected to the spark plugs. Crisis over.