Before 1980, the most common way of controlling the air and fuel that entered an engine consisted of a carburetor mounted on top of an intake manifold. As technology improved and emissions standards tightened, fuel injection became the standard system used because of its improved efficiency and ability to better control pollutant emissions. Fuel injection is a system that uses a throttle body for the purpose of controlling the fuel and air entering the engine.
The throttle body is responsible controlling the amount of air that flows into an engine. A valve is mounted inside the opening of the throttle body that opens and closes depending on input from the driver applied through the gas pedal. As the gas pedal is pushed down, the valve opens, allowing air to enter the engine. As the gas pedal is released, the valve closes, reducing the amount of air entering the engine.
Throttle bodies receives air from an assembly containing a filter that cleans the air and direct this air into the intake manifold. The intake manifold then mixes the air with fuel and directs this mixture to individual cylinders within the engine where the mixture is burned. Some throttle bodies operate differently; they mix the air and fuel on their own and deliver it directly to the cylinders through tubes called runners.
Throttle bodies have electrical components called mass airflow sensors mounted inside that sense the volume of air entering the engine. These sensors send information on the amount of air detected to the vehicle computer, which adjusts the amount of fuel added to the incoming air to maintain the proper fuel-to-air ratio for proper combustion in the engine cylinders.
Throttle bodies contain a sensor that monitors the position of the valve that controls airflow and the speed at which it opens. This allows the computer to note the position of the valve and helps the computer to determine the proper amount of fuel to add to the incoming air. The throttle position sensor also notes when the valve is opened quickly, allowing the computer to add more fuel to the incoming air, which improves throttle response and acceleration.
On some types of throttle bodies, the fuel injectors are mounted directly inside the throttle body. As the air controlling valve is opened, fuel is sprayed by an injector mounted in the throttle body directly into the incoming air stream. This mixture of air and fuel is then directed by the throttle body into the intake runners, where the mixture is delivered to the cylinders and burned. Some systems have a separate throttle body and injector for each cylinder.
