What was found
NR 1 ENGINE, DURING CLIMB THRU FL 250 TO 270, N1 FLUCTUATED BETWEEN 97-90 RPM. CENTER TANK FUEL EMPTY, TRANSFER FEEDING TO BALANCE 500LBS WING HEAVY RIGHT TANK. ENGINE ANTI-ICE ON, LASTED 90 SECONDS. AFTER LANDING NR 1 ENGINE CONTROL LIGHT CAME ON. ACFT GROUNDED. ACCOMPLISHED TASK 71-00-00-280-801-F00 THRUST INSTABILITY, ENGINE CONTROL LIGHT ON. ONLY FAULT 73-10331, CH-A, ENG-1, NOTED. ACCOMPLISHED TASK 73-06 TASK 809. ENG FUEL-N1,N2, EGT FAULT ISO. ACCOMPLISHED TC NG-73EO-11740, NO NEW FAULTS NOTED. COMPLETED SUPER SUMP IAW T/C NG-28EO-00002. NR 1 ENGINE CONTROL LIGHT RESET. NO FAULTS NOTED. VERIFICATION FLIGHT SATISFACTORY.