2001 Range Rover P38A. Put in a new car battery because car wouldn't start. After the new battery was put in the car started up with no problems but after a while of idling the car started to running hard and knocking. Turned the ignition off but the car continued to run on it's own. Had to disconnect the battery to cut it off. Without turning the ignition on, if I connect the battery it will start. Please help!