As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
COMPLAINT WAS 'MISFIRE' AT CRUISE POWER. SYMPTOM WAS NOSE YAW AT ERRATIC INTERVALS. NORMAL PREFLIGHT RUN-UP CHECK SHOWED NO PROBLEM. MAGNETO CHECK AT HOVER POWER CAUSED ENGINE FAILURE WHEN 'LEFT' MAGNETO POSITION WAS SELECTED. RECORDS INDICATE THIS COIL HAS BEEN IN SERVICE AT LEAST SINCE ENGINE MAJOR OVERHAUL IN 1987.