What was found
AIRCRAFT WAS GROUNDED: LEFT ENGINE N1 INDICATION DID NOT REACH PLANNED SETTING OF 95.3% FOR TAKEOFF. DISCONNECTED AUTO THROTTLE WHILE ACCELERATING DOWN THE RUNWAY. PUSHED LEFT THROTTLE FULL FWD AND ACHIEVED APPROXIMATELY 91.2 % N1. AIRCRAFT WAS ACCELERATING NORMALLY AND TAKEOFF WAS CONTINUED. ALL OTHER INDICATIONS ON BOTH ENGINES APPEARED TO BE NORMAL. LEFT ENGINE N1 INDICATIONS APPEARED TO CORRECT ITSELF SHORTLY AFTER TAKEOFF AND AUTO THROTTLES WERE PLACED ON.LEFT ENGINE OPERATED NORMALLY DURING REMAINDER OF FLIGHT. REPLACED LEFT ENGINE N1 SPEED SENSOR AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 77-11-01.