Dustin Corea come off the bench to net a 91st-minute equaliser as El Salvador deservedly drew 1-1 with Costa Rica in Houston on Saturday.
Costa Rica were far from their best in the CONCACAF Gold Cup Group B encounter at BBVA Compass Stadium, but Paulo Wanchope's men thought they had a priceless win wrapped up thanks to captain Bryan Ruiz's 60th-minute strike.
Ruiz fired powerfully into the bottom corner of the net for his 18th international goal - making him Costa Rica's eighth all-time leading scorer alongside Hernan Medford.
However, second-half substitute Corea ensured Costa Rica's winless streak extended to seven matches after restoring parity with his maiden El Salvador goal in the first minute of injury time.
El Salvador and Costa Rica are level on two points, two adrift of group leaders Jamaica, who edged Canada 1-0 earlier on Saturday, with one round of group fixtures remaining.
Wanchope drafted in Dave Myrie, Francisco Calvo, David Guzman and Alvaro Saborio following Costa Rica's 2-2 draw against Jamaica, with Junior Diaz, Cristian Gamboa, Jose Cubero and Johan Venegas making way.
El Salvador were forced to make one change, injured forward Nelson Bonilla replaced by Irvin Herrera in the starting XI.
Alberto Roca's El Salvador went into the match without a win in five matches against Costa Rica, a run spanning six years.
However, the El Salvadorians controlled proceedings for much of the first half.
Alexander Larin had one of El Salvador's best chances in the 23rd minute, after his low shot from an acute angle forced goalkeeper Esteban Alvarado into a save at the near post.
Arturo Alvarez and Herrera also had opportunities in front of goal, while Ruiz came close four minutes before half-time, with his volley flashing wide of the post.
Both defence's looked shaky in the second half, as Herrera and Saborio almost capitalised for their respective teams.
The deadlock, however, was finally broken by Ruiz on the hour-mark for his first international goal since last year's World Cup.
Played through by team-mate Saborio, Ruiz beat keeper Derby Carrillo at his near post with a powerful low effort.
El Salvador almost drew level via Moises Garcia in the 67th minute, who forced Alvarado into a fine save, while Darwin Ceren was unable to keep his volley underneath the crossbar, following a well-worked set-piece two minutes later.
The El Salvadorians were not to be denied a point, however, as Corea poked home Alvarez's cross with just three minutes of additional time remaining.
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