Comment by bombcar
2 years ago
Sounds like it might have been dieseling - enough carbon buildup glowing hot that even with both magnetos off it can still ignite the next rotation.
Usually there was a fuel disconnect along with the throttle that would eventually starve the engine.
That's probably what I did. Thinking back, the first time it happened, it just took about 10-15 seconds to shut off. The next time, when I was back at my home airport, it wouldn't stop running at all and I think I turned the fuel cutoff to get it to stop.