As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ENGINE NR 1 RPM UNSTABLE, REDUCED RPM TO 13,600. AIRCRAFT DIVERTED TO NEAREST AIRPORT. ENGINE WAS SHUTDOWN IN FINAL APPROACH, DUE TO RPM REDUCTION TO 13500 RPM. MAINTENANCE WAS SENT ON SITE AND FOUND THAT OIL PROPELLER FILLER PLUG WAS NOT SECURED PROPERLY AND ONE GALLON OF OIL HAD LEAKED OUT. PROPELLER REFILLED AND ENGINE RUN C/O (SERVICEABLE). AIRCRAFT RETURN TO SERVICE. (TC NR 20070816001)