What was found
DURING FLIGHT 2290 MKE-YYZ THE FLIGHT CREW REDUCED POWER FOR DESCENT. SHORTLY AFTER THE FLIGHT ATTENDANT REPORTED THE CABIN WAS FILLING WITH AN OIL SMELLING SMOKE. SHORTLY AFTER THAT THE FIRE DETECT SENSOR IN THE LAVATORY WENT OFF. THE CREW DECLARED AN EMERGENCY AND MADE AN UNEVENTFUL LANDING. MX INSPECTED AND RAN THE ENGINES AND DISCOVERED AFTER RUNNING THE LT ENGINE AT POWER FOR SEVERAL MINUTES THEN REDUCING POWER THE CABIN WOULD FILL WITH SMOKE. MX REPLACED THE LT ENGINE AND RETURNED THE A/C TO SERVICE.