As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLIMBING THROUGH FL 190, CREW HEARD A LOUD POP AND NOTICED THE LEFT ENGINE HAD DECREASED TO 1.35 EPR AND THE EGT HAD INCREASED TO 550. OPERATED ENGINE AT REDUCED POWER AND RETURNED TO LAND. REPLACED THE NR 1 ENGINE IAW DC-9 JOB CARD 9090010 AND DC-9 8A & 8B. OPS CHECKED GOOD.