What was found
WHILE PASSING FL265 CLIMBING TO FL300 NOTICED LP VIBRATIONS ON ENGINE 2. IT WAS APPROXIMATELY 4.2-4.4 AND RISING. DISCONNECTED AUTO THROTTLE AND SLIGHTLY PULLED BACK POWER ON NR 2 ENGINE. VIBRATION CONTINUED TO SLOWLY RISE TO AROUND 4.8. ADVISED ATC THAT A LOWER ALTITUDE WAS NEEDED AND WAS APPROVED TO DESCEND TO FL260. VIBRATION CONTINUED AROUND 4.5. DECLARED AN EMERGENCY AND DIVERTED TO COS. DURING DESCENT, VIBRATION REMAINED AT 4.2-4.4. LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED NR 2 ENGINE.