As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) #3 ENGINE BEGAN RUNNING ROUGH IN CRUISE. PRECAUTIONARY SHUT DOWN WAS CARRIED OUT. POST FLIGHT INSPECTION FOUND A SHORT TO GROUND HIGH TENSION LEAD FROM THE LEFT MAGNETO TO THE DISTRIBUTOR BLOCK. LEFT HIGH TENSION LEAD AND FRON TSPARK PLUG REPALCED. ENGINE GROUND CHECKED SERVICEABLE.