As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING WARM UP OF ENGINE, PILOT NOTED AN ABNORMAL SOUNDING ENGINE AND HIGH MANIFOLD PRESSURE. THERE WERE A FEW SMALL BACK FIRES NOTED. AFTER INVESTIGATION IT WAS DETERMINED THAT THE EXHAUST VALVE ON THE #2 CYLINDER WAS STUCK. THE CYLINDER WAS RECENTLY REPLACED AND APPEARED TO HAVE A TIGHT EXHAUST VALVE GUIDE FROM MANUFACTURE. THE EXHAUST VALVE GUIDE HAS SINCE BEEN REAMED TO PROPER SPECS AS PER LYCOMING SB388C. (TC# 20190622005)