Montero blasted the ball past Portland backup goalkeeper Joseph Bendik in the 56th minute, just seconds after Bendik subbed into the came in place of Donovan Ricketts, who was injured in the 51st after a nasty collision with Seattle's Eddie Johnson in front of the goal.
Earthquakes 2, Chivas USA 0 • In Carson, Calif., Chris Wondolowski scored on a penalty kick in the first half and Alan Gordon added a goal in the second half.
With the win, San Jose extended its Western Conference lead over Seattle to eight points, while Chivas is now tied with Portland for fewest in the conference.
Chivas coach Robin Fraser was ejected after the first half ended for arguing with a referee.
FC Dallas 1, Whitecaps 0 • In Frisco, Texas, Julian De Guzman scored in stoppage time to give FC Dallas a win.
FC Dallas now trails the Whitecaps by one point with the two clubs battling for the final playoff spot in the Western Conference. Vancouver has played one less game this season than FC Dallas, which won the season series 2-0-1.
Guzman fired a left-footed volley from 20 yards away, finding the bottom left corner of the net in the sixth and final minute of extra time for his first goal of the season. Guzman was acquired from Toronto on July 13.
Red Bulls 3, Crew 1 • In Harrison, N.J., Thierry Henry scored two goals and added an assist to lead New York to victory.
The victory enabled the Red Bulls to remain unbeaten at home this season and gave New York sole possession of second place in the Eastern Conference.
With 49 points, the Red Bulls temporarily moved past Chicago, two points behind front-runner Sporting Kansas City.