What was found
(CAN) IN CRUISE FLT, NR 2 ENGINE TORQUE DROPPED BELOW ENGINE TRIM ADJUSTMENT WITH POWER FLUXS. NR 2 ENGINE THROTTLED BACK FROM FLT TO IDLE. RETURNED TO GATE AS A PRECAUTION. ENGINE DECELED FROM POINT TO ACTIVATE REIGNITION SYS, & CONTINUED TO SPOOL DOWN TO APPROX 30 PERCENT N1, THROTTLE MOVED TO CUTOFF. A/C CONTINUED FLT IN OEI CONDITION FOR 30 MINUTES. PRELIMINARY INVEST SHOWED NO SIGNS OF EXTERNAL DAMAGE, FUEL, OIL, & AIR LINES INTACT, FUEL QUALITY CLEAN & CLEAR, FUEL FILTERS & SCREENS W/O MEASURABLE AMOUNT OF DIRT, & NO AIR IN FUEL SYS. NR 2 ENGINE ATTEMPTED START BUT WOULD NOT ACCELERATE PAST 31 PERCENT MARK ON TWO OCCASIONS.