What was found
DIAGNOSTICS REPORTS NR 1 ENGINE TREND DATA SHOWS A SUDDEN SHIFT IN EGT HOT DAY MARGIN. ACFT GROUNDED. PERFORMED FIM TASK 77-05-00-810-801-F00, STEP E (8) (B). RESULTS ARE S-1 83.56, S-2 63.34, S-3 62.51, S-4 109.20. TASK PERFORMED ON 3 HRS AFTER ENG NR 1 SHUTDOWN. FOUND S-4 READING FLICKERING, HIGHER AND OUT OF LIMITS. REPLACED S-4 PROBE REF MM 77-21-01. READING AFTER REPLACEMENT S-1 51.89, S-2 30.88, S-2 32.38, S-4 57.68. S-4. READING STEADY AND WITHIN LIMITS.