As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING APU TO PACK BLEED CONFIGURATION CHECK LEVEL AT 15000, ADJUSTING THRUST LEVERS CAUSED NUMBER 1 ENGINE TO HAVE SIGNIFICANT VISIBLE VIBRATION AS WELL AS COMPRESSOR STALL FELT IN FLIGHT DECK AND UNRESPONSIVENESS FROM LEFT ENGINE THRUST LEVER COMMANDS. GEAR WAS BEING TRANSITIONED BETWEEN DOWN AND UP DURING TWO OCCASIONS. **SUPPLEMENTAL REPORT WILL BE SUBMITTED**(OPEN).