What was found
SURGE OR STALL OF ENG DURING FWD THRUST. FELT AIRFRAME SHUDDER, OBSERVED EPR & N1 DROP & RECOVER. EPCS AUTO EVENT DATA SHOWS NO N1 OR N2 VIBE SHIFTS. FLIGHT CREW ADVISES N1 ROLL BACK WAS 1 - 3% & EPR ROLLBACK 0.15. FIM TASK 7 1-05 TASK 819 STEPS C12 & C13 CARRIED OUT, VISUALLY CHECK FOR METAL OR DAMAGE IN THE EXHAUST, FAN BLADES, FAN EXIT VANES, 2.5 & 2.9 BLEED VLVS. NO DAMAGE OR DEBRIS FOUND, ALL LOOK NORMAL.