Does the auto choke stay on the whole time the car ison?

No. Most, if not all, auto choke systems work off the temperature of the engine (usually the intake manifold). When the engine is cold, the choke provides a richer fuel mixture to aid starting and help smooth running. As the engine temp increases, the choke should slowly open. If the choke stays 'closed', fuel consumption will increase drastically, the engine's cylinders will become choked, the spark plugs may become coated with soot and fail to spark and the exhaust may emit smoke.