Do I need a choke?

To further elaborate:
There are three stages to most automatic chokes.
1. Initial choke with cold engine. This is the closed choke plate position for starting a cold engine. It will also link to a fast idle throttle position.
2. Qualified or cold running just after starting. As soon as the engine starts running, there should be enough manifold vacuum to pull the choke further open. The diaphram to do this may be visible or inside the choke.
3. Transition to warm running. As the engine warms the bimetal spring moves the choke plate further open. Slower idle is achieved through a link, and usually requires kicking the throttle to release the fast idle cam.