What was found
CREW REPORTED LT ENGINE WOULD NOT ACHIEVE CALCULATED TAKEOFF POWER N1. VERIFIED COMPLAINT, ENGINE COULD NOT ACHIEVE MORE THAN 94 PERCENT, N1 AND NOTED NO RPM DROP DURING EFC AUTHORITY CHECKS. ALSO NOTED FLUCTUATING ENGINE VIBRATION INDICATION. EFC AUTHORITY ADJUSTMENT HAD MINIMAL EFFECT, WOULD ONLY GET LESS THAN SPECIFIED 1.5 PERCENT N1 DROP, AND THEN COULD ONLY ACHIEVE 92 PERCENT N1. CHECKED T0 PROBE AND EEC, SWAPPED EEC'S, PROBLEM CONTINUED. REPLACED HMU (JET FUEL CONTROL) WITH OVERHAULED UNIT AND ADJUSTED ENGINE RIGGING AS REQUIRED, VERIFIED ENGINE PERFORMANCE NOW WITHIN MM SERVICE LIMITS. SUGGEST HMU MFG AND/OR ENGINE MFG TEARDOWN AND INVESTIGATE HMU FOR INTERNAL FAULT CAUSING LOW POWER, EFC AUTHORITY FAULTS.