When I Start My Car, the Engine Revs

Causes

Idle Air Control Valve (IACV)

The IACV is responsible for controlling the idle speed of the engine. When the engine is started, the IACV opens to allow more air to enter the engine, which increases the idle speed. If the IACV is faulty, it may not be able to control the idle speed properly, which can cause the engine to rev.

Throttle Position Sensor (TPS)

The TPS is responsible for telling the engine how much throttle is being applied. When the gas pedal is pressed, the TPS sends a signal to the engine, which opens the throttle body to allow more air to enter the engine. If the TPS is faulty, it may send an incorrect signal to the engine, which can cause the engine to rev.

Vacuum Leaks

Vacuum leaks can cause the engine to rev by allowing unmetered air to enter the engine. This can cause the engine to run lean, which can lead to increased idle speed.

Dirty Throttle Body

A dirty throttle body can also cause the engine to rev. When the throttle body is dirty, it can restrict the flow of air into the engine, which can cause the engine to run lean and increase the idle speed.

Diagnosis

To diagnose the cause of a high idle speed, the following steps can be taken:

1. Check the IACV for proper operation.
2. Check the TPS for proper operation.
3. Check for vacuum leaks.
4. Clean the throttle body.

Repair

The repair for a high idle speed will depend on the cause of the problem. If the IACV is faulty, it will need to be replaced. If the TPS is faulty, it will need to be replaced or adjusted. If there are vacuum leaks, they will need to be sealed. If the throttle body is dirty, it will need to be cleaned.

Prevention

The following steps can be taken to prevent a high idle speed from occurring:

• Regularly clean the throttle body.
• Check for vacuum leaks regularly.
• Replace the IACV and TPS as needed.

By following these steps, you can help to prevent a high idle speed from occurring in your car.