The Throttle Body

Note:  This content is directly from our Road Machines Educational CD, available for purchase and download instantly in our store.

Throttle Bodies:

Throttle bodies may have one or more valves for controlling the air entering the intake manifold. Valve angle is monitored by a position sensor. The engine computer uses the position information from the sensor to control fuel injection pulse time.

Throttle Valves:

The throttle valve (1) controls the amount of air entering the intake manifold and the level of vacuum in the manifold. A reduced valve opening causes a higher vacuum due to the engine trying to draw more air through than the valve will allow.

Throttle Position Sensor:

The throttle position sensor (2) is used by the engine computer for controlling fuel injection. The sensor is a variable resistor connected to the throttle lever shaft. As the valve opens, the computer lengthens fuel injection pulse time.

Idle Speed Control Solenoid:

The idle speed control solenoid (3) is controlled by the engine computer. The unit is an electric motor that displaces and holds the throttle valve at an angle determined by the computer to maintain the proper idle speed.