As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAH - FLT 4203, CREW REPROTED THAT DURING TAXI THE NR 1 ENGINE EMMITTED A HUMMING SOUND AND VIBRATION AT LOW TO MEDIUM POWER SETTINGS. MAINTENANCE REMOVED AND REPLACED THE NR 1 ENIGNE IAW ROLLS ROYCE MAINTENANCE MANUAL 71-00-00. THE AIRCRAFT WAS THEN APPROVED FOR RETURN TO SERVICE.