Grabavoy scored his first goal of the season in the 4th minute, putting RSL ahead to stay, and added his second in stoppage time as Salt Lake (6-5-2) notched its third win in four games.
Joao Plata and Robbie Findley also tallied in the victory.
Jorge Villafana scored in the 55th minute for Chivas (3-6-2).
Ray Liotta sues skin care company over use of likeness
Boston schools pull out free condoms over wrapping complaints