2003 Buick Century accelerates on its own have driven for over fifty miles using only the breaks. Park the car over night and its fine the next day. has done this 4 differant times in the last 30 days. Never when a repair shop is open.
Have you checked to see if the throttle mechanism is binding somewhere, and preventing the throttle from closing all the way?
[b]A defective Idle Air Control motor can cause unexpected acceleration.
If the IAC motor goes to the wrong position, it allows too much air into the engine. The oxygen sensor detects this extra air and trys to compensate for it by commanding the computer to add more fuel. More air, more fuel, and the engine accelerates on it’s own.
First check the throttle cable for fraying both at the throttle body and the gas pedal. Second if your car is equiped with cruise disconnect the cruise cable from the throttle body and see if the problem goes away.