What was found
EN ROUTE FRA/HKG, CRUISE CONFIGURATION AT FLT LEVEL 37K, CREW NOTICED MOMENTARY VIBRATION/RUMBLE, AND OBSERVED LOSS OF NR 2 ENGINE POWER (ROLL BACK). ENGINE INSTRUMENTS AT IDLE VALUES WITH N1 RPM ZERO. REPEATED THROTTLE CYCLING PRODUCED NO ENGINE RESPONSE. PERFORMED IFSD, ENGINE WINDMILLED WITH POSITIVE OIL PRESS (+ 5 PSI) FOR APPROX 3 MINUTES. ENGINE SUCCESSFULLY RE-STARTED AND OPS CHECK OK. NORMAL ENGINE OPERATION FOR DURATION OF FLIGHT TO ORIGINAL DESTINATION. UNSUCCESSFUL SPOOL UP AFTER MAINTENANCE AND RESTART ON GROUND, REMOVED AND REPLACED NR 2 ENGINE.