What was found
SEA FLIGHT 2380: ON FINAL APPROACH WHEN POWER WAS REDUCED TO FLIGHT IDLE, A SMELL OF OIL OF EXHAUST WAS COMING FROM AIR VENTS IN COCKPIT AND CABIN. AIRCRAFT WAS FERRIED TO PDX. MAINTENANCE C/W COMPRESSOR AND TURBINE WASH OF THE NR 2 ENGINE IAW Q400 AMM TASK 72-00-00-160-805. RAN ENGINES THROUGHOUT ALL POWER RANGES WITH BLEEDS SELECTED ON AND OFF. NO SMELL NOTED. PRIOR TO ENGINE WASH, NR 2 ENGINE WAS OVER SERVICED WITH APPROX 2 QUARTS OF ENGINE OIL. NO FURTHER DEFECTS NOTED. NO PARTS REPLACED. AIRCRAFT RETURNED TO SERVICE.