What was found
LFT - FLIGHT 2734, DURING PREFLIGHT INSPECTION, THE CREW REPORTED A BURNING SMELL IN THE COCKPIT. MAINTENANCE INSPECTED THE AIRCRAFT, AND FOUND THE ODOR TO BE COMING FROM THE PACKS WITH THE APU RUNNING. MAINTENANCE MEL'D THE APU 49-00-00 (C) CONTRO 128496, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE. ON 09/04/07, IAH MAINTENANCE RAN THE APU AND PACKS WITH NO DEFECTS NOTED, REMOVED THE MEL, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.