Tristan Bowen and Alex Cazumba also scored for Los Angeles (10-0-2), which tied its own MLS record for most games without a loss to start a season. The Galaxy opened 12-0 in their inaugural season.
Houston's Cam Weaver scored his first goal of the season in the 7th minute to tie the score at 1-1. The Dynamo (5-7-1) lost their third straight.
Kivorski gave the Galaxy a 1-0 lead just 47 seconds into the match, the third-fastest goal in Galaxy history and the second Los Angeles has scored in the opening minute this season.
Clint Mathis scored 33 seconds in for the Galaxy on July 25, 1999 and Brian Mullan did it 39 seconds in on May 9, 2001. A.J. DeLa Garza scored 51 seconds in against Philadelphia on May 1.
Kivorski put the Galaxy ahead for good in the 21st minute. Bowen scored in the 48th minute and Cazumba capped the scoring in the 56th.
The Galaxy, tops in MLS with 32 points, improved to 4-0 without stars Landon Donovan and Edson Buddle, who are with the U.S. national team preparing for next week's World Cup opener against England in South Africa.
The Galaxy have not played with Donovan and Buddle since a scoreless tie against Toronto FC on May 15.
Weaver's goal of the season proved to be a painful first-goal memory after taking a kick to the face from charging Galaxy goalie Donovan Ricketts. Los Angeles' Sean Franklin met Weaver at the top of the box, but moved out of the way for an oncoming Ricketts, who attempted to clear the ball. Lost in the collision was the ball, which trickled into the mouth of the goal to tie the match.