After repeatedly going to various mechanics to get a diagnosis throughout the years, they were all unsuccessful to find any report through the vehicle's computer. however, my car's engine is constantly revved up even when applying the brakes an slowing down causing it to jerk forward. this occurs suddenly and randomly when i am going at speeds below 20 mph including while on idle. if i neither apply the brakes nor the accelerator, it will still drive forward at 3 mph in rhythmic jerky waves. we took the vehicle to the local mazda dealer for a key replacement when we first purchased it, and i believe we reported the problem there first, but after the ridiculous service we got, i never wanted to return there again. this has been an ongoing issue since the beginning.