Q: Why Does an Engine Idle Fast or Slow?

asked by on

Why does an engine idle fast or slow?

A: Several factors can cause a fast or slow en...

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.

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

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: White smoke coming out of exhaust

White smoke is an indicator that the engine is burning coolant. The fact that the engine idles poorly points toward a problem with the cylinder head; most commonly, the head gaskets. When the gaskets fail, a leak between the cylinder(s),...

Q: Irregular revving

Is your Check Engine Light on? That may indicate that there is a diagnostic trouble code (dtc) stored. The code may help pinpoint which component requires further testing. Sometimes a dirty idle air control valve will stick during operation causing...

Q: Takes 3-7 tries before engine stays running

Hello. The symptoms you are experiencing, hard starting and an unstable idle speed, can be caused by a variety of issues. You mention that you replaced a few parts, namely ignition components, so they should be alright. The next things...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
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 P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...