What was found
(CAN) DURING TAXI, THE PILOT NOTICED THE NR 2 ENGINE ACCELERATING ON IT`S OWN. THE PILOT WAS ABLE TO STOP THE ENGINE ACCELERATION AND RETURNED TO DEPARTURE GATE SAFELY. THE FOLLOWING TROUBLESHOOTING WAS PERFORMED. WHEN THE ELECTRICAL POWER WAS PUT ON, NR 2 MANUAL CAUTION WAS ACTIVATED AND A FEW RESET PERFORMED. DURING GROUND TESTING, THE NH WAS REPORTED FLUCTUATING DURING START AND AGAIN THE ENGINE "RAN AWAY" ON IT`S OWN. THE EEC`S WERE SWAPPED, THE ELECTRICAL HARNESS WAS VERIFIED, ANOTHER GROUND RUN ATTEMPTED WITH SAME RESULTS. BEFORE SHUTTING DOWN THE ENGINE THE PLA WAS MOVED A FEW TIMES. AT NEXT ENGINE GROUND THE ENGINE PERFORMED NORMALLY. CUSTOMER ENGINEERING SUGGESTED TO REPLACE THE MFCU.