Throttle Body: Description and Operation

The throttle body consists of the main bore, air bypass passage, vacuum passage (for EGR system) and the following parts.
- Throttle valve which is interlocked with the accelerator pedal and controls the amount of the intake air
- Idle speed adjusting screw which controls the amount of bypass air to adjust idle air control duty (engine idle speed) (REFERENCE: Idle speed adjusting screw of new vehicle is adjusted full closed position.)
- Throttle position sensor which detects the throttle valve opening and sends a signal to ECM
- Idle air control valve which supplies the bypass air depending on engine condition.