As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(AUS) LT ENGINE POWER DOWN DURING PRE TAKE-OFF CHECKS. INVESTIGATION FOUND NR 4 CYLINDER UPPER SPARK PLUG HAD SEPARATED FROM THECYLINDER. CAUSE APPEARS TO BE FROM EROSION OF THE SPARK PLUG HOLE UNDER THE HELICOIL. SUSPECT FROM A VOID FORMED WHEN WELD REPAIRS WERE CARRIED OUT.