What was found
ON DESCENT APPROX 18000' FAS IN AFT REPORTED A DIRTYSOCK ODOR PRESENT FROM THE BACK OF THE CABIN TO THE MID EMERGENCY EXIT ROWS, FAS REPORTED ODOR DISSAPATED AFTER ABOUT 5 MINS, CAME BACK THEN DISSAPATED AGAIN. AFTER 5 MINS. PACKS WERE ON APU OFF. REPLACED NR 2 ENGINE. (LP 8793462 - AIRCRAFT WAS GROUNDED)