Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Air Intake System Description: Operation
| Callout | Component Name |
|---|---|
| 1 | Throttle Body |
| 2 | Air |
| 3 | Coolant |
| 4 | Idle Air (Bypass) Passage |
| 5 | IAC Valve |
| 6 | Coolant Passage |
| 7 | Magnet |
| 8 | Rotary Valve |
| 9 | Throttle Valve |
The PCM uses the IAC valve in order to control the engine idle speed. The PCM communicates with the IAC valve by varying the ON time of a repeating ON/OFF duty cycle. A magnet inside the IAC valve operates a rotary valve that controls the opening of the idle air bypass passage in the throttle body. The idle air passage allows air to enter the engine without passing over the throttle valve. The strength of the magnet in the IAC valve is related to the current flow in the IAC circuit.
The PCM increases the ON time of the IAC valve command in order to increase the idle air passage opening. A larger idle air passage opening allows more air to enter the intake resulting in an increase in engine speed.
The IAC valve contains an engine coolant passage that enables the IAC valve to operate more efficiently at cold temperatures. The IAC valve enables the PCM to easily control engine idle speed by precisely metering the engine's air intake at closed throttle.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.