As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, NOTED ENGINE WAS RUNNING ROUGH. DID NOT REPORT ANY POWER OR RPM LOSS. DECIDED TO DISCONTINUE FLIGHT. MAINTENANCE RAN THE ACFT ON GROUND AND DID NOT EXPERIENCE ANY ROUGHNESS, A VISUAL EXAMINATION OF THE ENGINE'S ACCESSORIES REVEALED THE MAGNETO TIMING HOUSING WAS CONTAMINATED WITH OIL. REPLACED, AND SUBSEQUENT ENGINE GROUND RUNS WERE SATISFACTORY.