Throttle body

The throttle body is the part of a fuel-injected engine's intake that does the carburettor's job, except it doesn't mix the fuel itself. It contains the throttle valve, which opens as you twist the grip to let more air into the engine; an electronically controlled injector adds the fuel.

The body usually carries a throttle position sensor (TPS), which the ECU uses to calculate fuel quantity, plus idle air control. On ride-by-wire systems an electric motor opens the valve instead of a throttle cable.

On multi-cylinder engines the throttle bodies need synchronising from time to time so every cylinder gets the same airflow – this gives a smoother idle and throttle response. A dirty throttle body causes an uneven idle; clean it carefully with a dedicated cleaner.