A choke is a device which richens the air/fuel mixture during a cold start on vehicles fitted with a carburettor. They are now practically obsolete.

The choke or choke flap is fitted to the upstream end of a carburettor intake and restricts the amount of air entering the carburettor. This makes the air/fuel ratio richer, which is required for reliable cold starting.

Chokes are often controlled by a lever or knob on the dashboard, steering column or steering wheel hub, but an automatic choke is controlled by a temperature sensitive bi-metallic strip.

Excessive use of a choke can result in premature engine wear, as the large amount of fuel in the combustion chamber washes away lubricating oil from the bores and piston rings.