As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EN ROUTE SJU-MCO, NR 1 ENGINE N1 VIBRATION CYCLED BETWEEN 4.0 AND 9.8. WHEN ENGINE REDUCED TO IDLE, ENGINE VIBRATION STOPPED. CAPTAIN DECLARED EMERGENCY AND AIRCRAFT LANDED AT MIA WITHOUT INCIDENT. REPLACED LEFT ENGINE JOINT. SYSTEM GROUND CHECKED NORMAL OPERATION. (M)