Cahill headed a rebound in the 80th minute after Andy Gruenebaum made the initial save off a shot by Jonathan Steele.
New York (5-4-2) has won three straight.
Columbus (3-3-3) had its 12-game home unbeaten streak ended.
IMPACT 2, EARTHQUAKES 2
SANTA CLARA, Calif. -- Sam Cronin scored in the first minute of second-half injury time to give San Jose a draw against Montreal.
Cronin took one touch off a knockdown header from Chris Wondolowski and lashed a shot home from 20 yards for his first goal of the season.
Montreal (5-1-2) extended its unbeaten streak to three matches.
San Jose (2-3-5) has tied four of the past five matches and is winless in six straight games.
SOUNDERS 2, UNION 2
CHESTER, Pa. -- Mauro Rosales scored a goal in the 64th minute to give Seattle a draw on the road against Philadelphia.
Danny Cruz scored twice for the Union (3-3-3), who remained undefeated at home.
Five minutes later, Seattle's DeAndre Yedlin was sent off at the beginning of stoppage time.
REAL SALT LAKE 2, WHITECAPS 0
Salt Lake (4-4-2) played without its top three forwards as Alvaro Saborio, Robbie Findley and Olmes Garcia all were sidelined because of injuries. It forced head coach Jason Kreis to use his ninth different starting lineup this season.
The Whitecaps (2-4-3) extended their MLS winless streak to seven games. Vancouver has not won since a 2-1 home victory over Columbus on March 9. The Whitecaps have given up at least two goals in five of those seven contests.
RAPIDS 1, TORONTO FC 0
COMMERCE CITY, Colo. -- Edson Buddle scored in the 86th minute to lift Colorado.
After finding the ball just outside the crease when Toronto defender Logan Emory gave it up, Buddle easily scored into the back of the net for his first goal of the season.
Colorado (3-4-3) has scored four goals in its past five games, though the Rapids have been outscored 9-8 overall this season.
Rapids goalkeeper Clint Irwin outplayed Toronto's Joseph Bendik to improve to 3-2-2 with three shutouts since taking over for the injured Matt Pickens.
Toronto (1-4-4) has lost consecutive games after tying four straight, and dropped to 0-3-1 on road.
Copyright 2013 by The Associated Press
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