More detailed specifications and instructions are printed in shop service manuals at car dealers nationwide or found in your local public library. Auto part stores should also have these specifications for your car. Over the years, moving parts on the carburetor become worn, passages become blocked by sediment, the gaskets and diaphragms deteriorate. When these things happen, it must be cleaned and rebuilt, or replaced. Most of the time, it is just the choke that needs adjustment.
Most cars have an automatic choke, which slowly opens as the engine warms up.
Tap the accelerator pedal when the engine is cold, the choke should open by just a crack. After 5 minutes of running the engine, the choke should be opened fully. Remove the air cleaner to observe choke operation. With the engine cold, tap the gas pedal once. The choke plate should close fully.