We had a TR6 in the other day that would start and drive okay and then cut off, inexplicably.  Chip removed the distributor cap and found this:

Bad Triumph TR6 Distributor Rotor

If you’ve been here a while, you’ll recognize the maligned rotor with a rivet, the subject of this earlier post. Chip installed the improved rotor. He may have done something else, too, not sure. The car runs much better now. If your car is moody, put the rotor button on the checklist.