What was found
ON FLIGHT 4467 THE CREW REPORTED THE ECS SYSTEM SMELLED OF OIL. INSPECTED AND VERIFIED THE SMELL IS FROM NR 1 THE AIR CYCLE MACHINE NOT FROM ENGINE OR APU BLEED SOURCES. PERFORMED ENGINE RUNS PER EMB MM 72-00-00. NR 1 AIR CYCLE MACHINE DEFERRED PER (EMB) AEA MEL. INSPECTED NR 1 AIR CYCLE MACHINE AND RAN UP ENGINES TO TROUBLESHOOT SMELL IAW FIM TASK 21-20-00-810-801-A AND 72-00-00-810-808A. FOUND NO ODOR SMELL DURING RUN-UP. THE OPERATIONAL CHECK OF NR 1 AIR CYCLE MACHINE WAS GOOD IAW EMB AMM 21-00-00. THE AIRCRAFT WAS RETURNED TO SERVICE.