As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED. DURING TAXI OUT, THE TOWER, CREW, PASSENGERS AND ANOTHER ACFT OBSERVED FLAMES COMING FROM THE NR 1 ENGINE TAIL PIPE. NR 1 ENGINE SHUTDOWN AND ACFT RETURNED TO GATE. MAINTENANCE OBSERVED OIL IN THE TAIL PIPE AND DURING ENGINE RUN FLAME FROM EXHAUST PLUG. R & R NR 1 ENGINE IAW MCM CARD 71-94-01. LEAK AND OPS CHECKS NORMAL.