As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) PILOTS NOTED BANGING NOISE COMING FROM ENGINE AT LOW IDLE. ENGINE SHUTDOWN, COWLING WAS REMOVED. HEAT MUFFLER SHROUD WAS FOUND BROKEN AND BANGING AGAINST ENGINE MOUNT. HEAT MUFFLER WAS INSPECTED FOR DAMAGE NONE WAS FOUND. NEW HEATER SHROUD WAS INSTALLED. COWLING REPLACED AND ENGINE RAN UP, NOISE WAS NO LONGER THERE.