Date: 201704
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: Rain
Light: Daylight
Aircraft: A321
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Parked
ATC / advisory: Ramp ZZZ
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: Aircraft In Service At Gate
Result: General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: We were at the gate; running about five minutes late (past departure time) due to several maintenance items that were in the paperwork phase at the time of departure. About that time; a storm cell arrived from the NW and it began raining heavily. The oily fume odor began as a very slight odor. At first; I was in denial. I thought - it's so minor; it will go away. Besides; the plane was loaded; and I'd already had to call MX control several times for other items; we just HAD to go. But the smell grew stronger. The FO (First Officer) smelled it; the FA's (Flight Attendants) in the forward galley smelled it. A front row passengers asked a FA about it. The mechanic was still there; I asked him if he smelled it. There was a faint fogginess down the aisle. We tried various combinations of L&R packs off one; at a time.Usually; in humid climates (or during a rain storm); I have seen condensation flowing in the 'cove' areas of the cabin; between the upper wall and the overhead bins; rolling down the passenger windows like a gentle misty waterfall. But it's rare that I've ever seen it in the aisle. No apparent source; just hanging in the aisle.So we asked the passengers to gather their items and deplane. The packs were turned off & the mechanic took over from there. I asked the FA's to deplane promptly as well; and asked about symptoms. I think all FA's had smelled the fumes odor; and at least two or three had either a sore/raspy throat and/or mild burning/itchy eyes. I noticed a slight lightheadedness myself; that lasted about two hours. After less than an hour (approx 15-20 minutes for deplaning; approx 20-30 minutes while the mechanic ran the engines at idle at the gate); I was asked to go back to the plane to do a sniff test. Despite the forward cabin doors being open; the fumes odor was still present in the forward cabin (and the jet way for that matter); and to a much greater degree on the flight deck. After less than a minute on the flight deck; I felt a recurrence/strengthening/renewal of the lightheaded feeling I had been feeling after the initial onset on the fume event.Two mechanics took the aircraft to the hardstand & ran the engines at a high thrust setting. They returned to the gate and the flight was cancelled because the fumes odor was still present. The next morning; I met the [previous] crew at breakfast at the hotel. They had brought the plane to us; and were supposed to have flown the aircraft [the following] morning. Their flight in [this aircraft] had been delayed; waiting for mechanics to arrive and fix the problem. When we arrived [the aircraft] was still there.




Synopsis: A321 Captain reported a fume odor at the gate that after several maintenance engine runs still persisted and the flight was cancelled.