Houston (10-5-7) got all the scoring it would need just before halftime when Brad Davis sent a corner kick to the near post and Bobby Boswell forwarded it to the back post where a wide-open Carr headed it in.
It was the third goal in three matches for the Houston striker.
Davis also assisted on the Dynamo's second tally in the 86th when Ching netted his fourth of the season, securing Houston's fourth straight victory.
Toronto (5-12-4) fell to 4-3-4 since June 7 when Paul Mariner took the reins as head coach.
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