Women's FA Cup holders Manchester City needed extra time for the second round in a row but avoided a shock exit at fellow top-flight side Sunderland.
The league title hopefuls were heading out of the cup before Jane Ross' close-range 90th-minute equaliser saved them.
Victoria Williams had given the hosts a shock lead against the run of play, Demi Stokes levelled for City, but Lucy Staniforth restored the lead.
Ross and Ella Toone struck either side of half-time in extra time to win it.
Victory set up a semi-final at Women's Super League 1 leaders Chelsea on 15 April, which will see the two rivals meet in a major domestic semi-final for the fifth time since 2014.