What was found
DTW FLT 902 EN ROUTE CLT TO DTW, DURING DESCENT, BELOW FL 290, ENGINE 1 BEGAN TO RUMBLE AND VIBRATE. THE AUTOTHROTTLE WAS DISCONNECTED AND THE NUMBER 1 ENGINE WAS BROUGHT BACK IDLE AND THE VIBRATIONS STOPPED. AT 7,000 FEET AND 210 KNOTS, THE AUTOTHROTTLES WERE RE-ENGAGED AND ALL OPERATIONS WERE NORMAL. AFTER LANDING AND ARRIVAL AT THE GATE, THE GROUND CREW NOTICED A TRAIL OF FUEL THAT FOLLOWED THE NUMBER ENGINE, ENDING IN A PUDDLE UNDERNEATH IT. ALSO, A 1,000 POUND DIFFERENCE IN FUEL BURN BETWEEN THE LEFT AND RIGHT FUEL TANKS WAS NOTED. MAINTENANCE FOUND THE NUMBER 1 ENGINE HMU LEAKING. THE HMU WAS CHANGED WITH THE ENGINE. THE ENGINE WAS CHANGED DUE TO OTHER PERFORMANCE ISSUES NOT RELATED TO THE FUEL LEA