As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED A SOUR OILY SMELL COMES FROM THE AIR VENTS, WHEN THE LEFT FLOW WAS TURNED ON. UPON INVESTIGATION MAINTENANCE FOUND THE LEFT AIR CYCLE MACHINE TO BE OVERSERVICED. THE ACM WAS RESERVICED AND THE AIRCRAFT WAS RETURNED TO SERVICE WITH NO FURTHER PROBLEMS.