As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING CRUISE THE FLIGHT CREW NOTICED NR 1 ENGINE WAS BACKFIRING. THE ENGINE WAS SHUT DOWN AND THE PROPELLER WAS FEATHERED. THE AIRCRAFT RETURNED TO BASE. MAINTENANCE CREWS FOUND THE INTAKE INSERT ON NR 11 CYLINDER WAS LOOSE. THE CYLINDER WAS REPLACED WITH A SERVICEABLE ASSEMBLY. THE ENGINE WAS GROUND RUN AND LEAK CHECKED SERVICEABLE. THE AIRRAFT WAS RETURNED TO SERVICE.