What was found
ON TAKEOFF USING 24K REDUCED POWER (92.1 N1) LEFT ENGINE WAS MOVING BETWEEN 90 N1 93 N1. AUTOTHROTTLES DISENGAGED REDUCED POWER TO APPROX 75 PERCENT N1 AND ENG RAN NORMAL. HOWEVER WITH AT OFF AND POWER AT 25K (CLIMB POWER) ENGINE STILL FLUCTUATING. RETURNED TO SEA. N2 & FF WAS ALSO FLUCTUATING. DIVERSION TIME: 13 MIN. RAN NR 1 ENGINE PER AMM TASK 71 00 00 800 807 F00. EXPERIENCED N1 N2 FF AND EGT FLUCTUATION AT 65 PERCENT N1 AND 91 PERCENT N1. DISCONECTED EEC FLUCTUATION CONTINUED. REPLACED T12 SENSOR ON NR 1 ENGINE PER MM 73 21 05 400. NO FLUCTUATIONS AT POWER NO EEC FAULTS. REPAIR CONFIRMED PER FIM 73 06 00 810 STEP F.