UNINTENDED SURGE IN ACCELERATOR. I WAS REVERSING INTO A PARKING STALL IN THE GARAGE OF A CONDO COMPLEX. THIS IS A COMPACT STALL WITH ONLY ABOUT EIGHT INCHES OF SPACE FROM THE TIRE TO THE DIVIDING LINE, SO I NEED TO PARK VERY CAREFULLY AND SLOWLY. ONCE THE VEHICLE WAS IN MOTION AND I WAS PARTIALLY INTO THE PARKING STALL, I RELEASED MY FOOT FROM THE ACCELERATOR, PREPARING TO WORK MY WAY INTO THE STALL. INSTEAD OF SLOWING DOWN, THE CAR SURGED BACKWARDS AT A MUCH HIGHER SPEED. THE VEHICLE RAMMED AND BOUNCED OFF A CONCRETE WALL WITH GREAT FORCE. THE TIRES HAD SQUEALED BEFORE THE IMPACT. THE VEHICLE ENDED UP IN ABOUT THE SAME POSITION THAT IT WAS IN BEFORE THE ACCELERATOR SURGE.