As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER GEAR UP, INDICATION OF SMOKE IN THE BACK. NO SMOKE VISIBLE BUT STRONG SMELL. MX INSPECTED AC DUCTS AND CLEANED. PERFORMED ENGINE RUNS. APU STARTED AND OIL SMELL CAME BACK. APU BEING WORKED ON. MX WILL ALSO INSPECT LAV, RETURNED TO SEAT LIGHTED PLACARD, BECAUSE OF OTHER SIMILAR EVENTS ON FLEET.