Car Throttle Stuck problems of the 2004 Lexus IS300

Car failed to stop at a red light under normal braking because engine failed to decelerate when pressure was removed from the pedal. Maximum force was applied to the brake pedal. The brake anti lock feature was activated and a collision with the stopped car ahead was barely averted. When stopped, the engine reverted to normal idle. The problem did not recur. Examination by a mechanic at the dealers shop failed to identify a computer fault or other cause. The car was returned without repair. I am not satisfied that a stuck throttle is not a repairable or abnormal condition. It seems to me be highly dangerous and merits more than a "well, its working now so come back when if it happens again. " sort of response.