What was found
SFO - DURING CLIMB-OUT THROUGH 10,000 FEET, POWER LEVER SPLIT REPORTED. AT 14,00 FEET, LEFT POWER LEVER FAILED TO CONTROL ENGINE POWER. CREW SECURED LEFT ENGINE AND RETURNED TO STATION WITHOUT INCIDENT. MAINTENANCE FOUND LEFT ENGINE HMU INPUT SHAFT NUT LOOSE. RIGGED INPUT SHAFT, TIGHTENED AND SECURED INPUT SHAFT NUT. POWER LEVER CONTROL NORMAL ON ENGINE GROUND RUN. AIRCRAFT RETURNED TO SERVICE. (X)