why does my accelerator cable not retract when i let off the pedal?

Based on the year of the vehicle you may have carbon build up in the throttle body causing this problem. If it is the cable as you say or the carbon build up as I say it should happen all the time. If you know how to remove the air cleaner from the throttle body go ahead and do so then look inside at the plate while you move the part that the gas pedal cable is attached to. This is done with the car off. If it is the cable as you say it may have worn through the plastic and is hanging up on it or there may be a problem where the cable goes into the plastic sleeve either at the gas pedal or at the throttle body. Also check to be sure the gas pedal pivot isnt causing your problem it may just need to be lubricated.