You start your car engine early on a cold morning to allow the temperature to warm up before you get inside. Or you run inside a store and leave the engine running. When this happens, your car’s engine is idling. This complex task is important, and the engine must not run too high or too low to ensure no parts are damaged.
Why engines run high or low
An engine can run high for various reasons. Some performance engines, such as those installed in racing cars, are designed to run higher. Another reason is when you turn on the air conditioning or when the engine is running multiple systems, it must run at a higher speed to keep everything going smoothly.
Running low can be a problem because it may not allow the oil pressure to be at a high enough point. The components will wear faster and the engine may even seize or lock up.
How the engine idles
The idle air control motor valve controls the idling of the engine. When it fails or begins having problems, the impact will change the idle speed of the engine. Intake gaskets and vacuum hoses also help monitor the engine idle speed, and they can have a negative impact if they are worn or damaged.
Another important component is the air intake boot. Its job is to move air that comes into the engine intake system. When it’s damaged, more air can be passed through, which will cause the engine to idle fast or slow. A damaged throttle bore will result in the same problem because it’s supposed to regulate the volume of air flowing into the engine.
The PCV valve or crankcase ventilation system removes vapors from the engine. When it doesn’t work correctly, the engine may idle at various speeds. The idle speed also comes from engine timing. When it isn’t timed correctly, the result is an engine that idles too fast or too slow. All of these components can cause a problem with idle speed when they don’t work correctly. If your engine is idling too fast or too slow, a technician needs to inspect the system to determine which component is at fault.
This article originally appeared on YourMechanic.com as How Does an Engine Idle High and Low? and was authored by Joyce Morse.