B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Flight Crew Last 90 Days 169; Flight Crew Total 15400; Flight Crew Type 6440
Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance
Flight Crew Rejected Takeoff; Flight Crew Returned To Gate; General Flight Cancelled / Delayed; General Maintenance Action
Procedure; Aircraft; Human Factors
After advancing the thrust levers and verifying symmetric thrust; I engaged the auto throttles and monitored the advancement of thrust to the specified value. Engine 2 thrust increased to the value specified for the takeoff; 102 pct. With thrust levers matched; engine 1 thrust did not increase above 95 pct. I rejected the takeoff at about 50 kts. We cleared the runway; performed the [Rejected Takeoff] checklist; and returned to the gate. I sent an ELB entry describing the discrepancy.Based on review of this aircraft's maintenance history; the same or similar thrust discrepancy was squawked on the two previous flights. Before our departure; ZZZ Maintenance explained the history; stating that they had successfully run the engine up to about 90 pct N1 but could not test greater thrust on the ramp. They showed me engine data from the preceding takeoff indicating that the low N1 value was accompanied by low fuel flow; EGT; and N2 values. They replaced the N1 sensor and released the aircraft for our flight. With this information; it was not a surprise during our takeoff to see Engine 1 not developing the thrust specified on the takeoff performance up link.
B737 Captain reported a rejected takeoff caused by engine 1 not making required power.