What would cause my car to jerk and stahl out when stopping?

Ive been told my idol control valve is causing my check engine light to come on after it was put on a computer at auto zone and it cuts off when stopping but today while stopping and attempting to downshift it jerked extremely hard and cut off. I drove it about a block to the house and let it sit then attempted to start it and it would start with my foot all the way in the gas rev to four rpms and die out.