 My throttle has stuck on multiple occasions.  Dealership has no idea of cause. I have eliminated cruise control and floor mat possibilities. The automatic transmission occasionally drops down two gears at a time causing a sudden deceleration and alarming thump when letting of gas and gently applying brakes.  other than this, it is the best car I have ever owned.  Incredible gas mileage when using cruise control and gasoline without ethanol. (31 mpg) from a 260 hp v6.  Handles like a sports car.  rides like a caddy.