Skip the auto shop - Our mechanics make house calls

Q: Why Does an Engine Idle Fast or Slow?

asked by on

Why does an engine idle fast or slow?

Several factors can cause a fast or slow engine idle. Running the air conditioning or defroster will speed up the idle speed of the engine. Components that impact the engine idle speed include the idle air control motor valve, air intake boot, and PCV valve or crankcase ventilation system. Monitoring the idling of the engine can prevent other issues and long-term damage.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Car coughs while driving.....sometimes.

Hi there. There are multiple potential causes of your engine's "cough". The engine that powers your 2007 Honda City has multiple sensors that help the fuel system burn fuel efficiently. Since your fuel efficiency mileage is also suffering, my...

Q: Stalling and erratic idle

Hi Dean, I believe you are correct in that you may have a dirty or faulty idle air control valve. The idle air control valve is a small valve on the engine's intake system that reads the air intake as...

Q: Car idles rough with AC on - 2008 dodge avenger

Hello, thank you for writing in. There can be multiple problems with the vehicle causing your issues. First, we need to take a look at the drive belt which sends power to the AC system from the engine. When the...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.