1. Verify the Engine’s Temperature
Make sure the engine is cold. If the engine is hot, switch off the engine and let it cool down. When the engine warms up, it could lead to a change in idle speed. When the engine is properly warmed up, then you can carry on with the adjustment process.
2. Connect a Tachometer
Connect the tachometer to the engine. This is vital since you will need to observe the engine RPM as you move forward with the adjustment process. For the most precise reading, connect it straight to the ignition terminal connector.
3. Locate the Idle Air Control (IAC) Screw
The next step is to locate the IAC screw. If you haven’t already, read through your vehicle’s repair manual to help locate the IAC screw easily. It is typically at the throttle body.
4. Start the Engine
Switch on the engine and allow it to idle for about a minute. This warms the engine up, leading to a proper RPM reading that will be handy during the adjustment. As the engine idles, make sure you observe the RPM reading.
5. Adjusting the RPM
While you’re observing the RPM, use a screwdriver to turn the IAC screw either clockwise or anticlockwise. As you do this, pay close attention to how the RPM adjusts. Turning the IAC screw clockwise results in a higher RPM reading, while turning it anticlockwise lowers the RPM. Once you’ve achieved the recommended idle speed for your engine, hold the IAC screw in that position.
Note: If you find it challenging to get the precise RPM when adjusting with the screwdriver, you can consider using a socket and ratchet.
6. Switch off the Engine and Lock the Screw
Finally, switch off the engine. This keeps the IAC screw from spinning out due to vibrations from the engine.
