Recent craziness: Sunday I cleaned the throttle body - all nice and shiny. Also, I got in all the parts and replaced the jumpered heater core hose with new Volvo hoses and a heater valve. I even flushed the coolant.
I replaced the sparks, but not the wires. The wires are newish, but not OEM. I do have a set of older, good condition OEMs off the junk yard wagon.

Monday, drove better than ever. Cheap gas and no tapping or other funny noises. More power. Very happy camper.

Today I started her up - no issues. I got about 4-5 miles down the road and, while doing about 40mph, it quit, started right up, quit, started, etc. The engine was not under load as I was headed down a slight hill.

The tach was the main sign. It was running so smoothly that I had no indication of issues except the tach would bottom out then jump back up to about 2K.

At the traffic light, it died. :(

I shoved it a little and got to the median under an overpass (nice shade) where I proceeded to poke about at the things I had worked on.

I pulled the spark wires, nice click coming off and going back on. I fidgeted with them at the distributor - sticky, but then clicky.

I tapped the fuel relief valve on the rail - plenty of gas there.

I played with the wire to the ignition coil, seemed ok. Tugged on the pos and neg at the battery - well connected.

Tried ignition and it started right up.

I hurriedly headed for home and made back about 2 miles. I was doing about 40 again, flat road so medium load on engined and same symptoms - on/off/on/off and dead. I dropped into neutral and made it to a parking lot.

Does this sound like a relay? Like a dead ignition coil?

Thanks for any input.