Diego Valeri and Will Johnson also scored for the Timbers (4-1-6), who extended their club-record unbeaten streak to nine games.
The victory moved Portland into sole possession of second place in the Western Conference with 18 points.
Chivas (3-5-2), meanwhile, logged its fifth straight game without a victory.
The Goats have allowed nine goals over a three-game span.
Celebrity Couples of 2014 [PHOTOS]