What was found
PACK AIR PRESSURE IS WEAK WHEN USING APU BLEED. WHEN ON ENGINE BLEED AIR SMELLS BAD DEBRIEF CREW. NOTED ODOR ONLY (NO SMOKE) ON TAKE OFF, CRUISE NORMAL, DESCENT ODOR RETURNED. NO ODOR NOTED BY F/A'S. PERFORM SMOKE/ODOR IN FLIGHT DECK/CABIN- CONDITIONAL INSPECTION. IAW AMM 05-51-26-800-891-C1. EEC 1 & 2 BITE NORMAL. PACKS RAN NORMAL ON GROUND WITH APU. NO ODORS NOTED. OPEN BOTH PACK BAYS, NOTHING NOTED. PERFORMED 1 & 2 ENGINE RUNS IAW AMM 71-00-00-201. ISOLATE ENGINE BLEED SOURCE DURING PACK TEST. NO ODORS NOTED. AC HAD PCI ENG WASH DONE AT BNA ON THE 28TH. OPS CHKD NORMAL. NO HISTORY. ACFT BACK TO NORMAL CONFIG. ACFT OK TO CONTINUE.