As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
REMOVED SPARK PLUGS FOR O/H AND REINSTALLED IN AUGUST 2012 AFTER O/H. RAN UP ENGINE FOR OIL CHANGE, NOTICED THE ENGINE WAS MISSING ON THE RT MAG DURING MAG CHECKED. REMOVED PLUGS TO CLEAN AND GAPPED AND FOUND NR 3 CYLINDER BOTTOM SPARK PLUG INSULATOR BROKEN. BORESCOPED ENGINE FOR ANY DEFECTS AND NO DEFECTS NOTED AT THIS TIME.