What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS ON DESENT TO PHX ACRID SMELL IN FLT DECK SELECTED PACK 1 OFF ODOR DISAPATED. MAINTENANCE TROUBLESHOT IAW JOB CARD 26L00021001, FOUND EVIDENCE OIL LEAK FROM APU. AFTER FURTHER INVESTIGATING AND MULTIPLE BURNOUTS NO LEAKS NOTED ON APU, THE SOURCE OF ODOR WAS CAUSED BY A PRE-EXISTING CONTAMINATION. JOB CARDS 26L00021002, AND 26L00021004 DECONTAMINATION ECS. NO ODOR IN FLIGHT DECK OR CABIN NOTED.