Portland's Sal Zizzo put a corner kick to the near post for Kris Boyd, who moved the ball to the front of the net where it bounced off the knee the Fire's Pause and into his own goal, breaking a 1-1 tie.
Eric Brunner registered first goal of the season in the 20th minute for the Timbers (3-5-3), who logged their first win in four games.
Jalil Anibaba netted the equalizer 19 minutes later for Chicago (4-3-3), which had a three-game unbeaten streak snapped.
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