A321
Flight Crew Air Transport Pilot (ATP)
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Speed All Types; Inflight Event / Encounter Unstabilized Approach
Flight Crew Executed Go Around / Missed Approach
Aircraft; Human Factors
During approach to LAX we received a late change of runway; from 24R to 25L. We were a bit high when we were cleared for the approach to 24R and then changed to 25L.  Approximately 10 miles out we slowed to 200 and configured the jet. There was an uncommanded power surge and we decided to go around. The reason for the go around was the uncommanded power surge and we were not stable. We cleaned up the jet as soon as possible and did a go around back to a normal landing at LAX.  After the fact FOQA informed me that there was a gear over speed. Neither myself nor the FO were aware of this. This is the second time that I have had an uncommanded power surge after a runway change at LAX. Both resulted in [a] go around to a normal landing.
We received a late change of runway; from 24R to 25L; while on base to final at LAX. I made the necessary changes in the MCDU as the Captain slowed the aircraft. We discussed that it would be difficult to configure the aircraft; descend and slow in adequate time to fly a stable approach. Once on final; we lowered the landing gear and selecting flaps one. The Captain; in an effort to further slow the aircraft; selected the Approach speed mode. At this moment; the aircraft began to accelerate; as if going to climb speed mode rather than approach speed mode. To the best of our knowledge and recollection; we had selected Approach Mode prior to the runway change.Already in a difficult position to achieve a stable approach; the Captain announced the Go Around. He momentarily selected TOGA and back to Climb on the thrust levers. We immediately cleaned up the aircraft but the gear did not complete retraction within airspeed limitations; thus the Gear Overspeed. We brought the aircraft around for an uneventful landing.
A321 flight crew reported executing a go-around after experiencing uncommanded thrust on approach to LAX.