Why is My Car Idling So High?

Have you noticed your vehicle idling high at stop lights or while parked? Maybe you’ve noticed your engine sounds louder or less happy than normal. There are various reasons your vehicle could be experiencing these issues. In this article, we’ll cover some of the most common sources of a high idle, and what you should do in this situation. 

What is a “High Idle”?

Usually, gasoline vehicles idle at somewhere around 750 RPM. This means that the engine is running at a healthy speed and is using a minimal amount of fuel. Idle speeds over 900 RPM could mean that your vehicle has an issue as well as using an excess amount of gasoline. Some issues can even leave idle speeds over 1300 RPM. 

It’s also important to note that different engine sizes will have different normal idle levels. Generally, the larger the engine, the lower the idle speed will be. If you’re unsure what yours should be, consulting a trusted professional is always a good way to ensure your vehicle is running the way it should. 

Glowing tachometer

What Problems Does a High Idle Cause?

A high idle can cause your vehicle to act in unusual ways, including:

  • Engine sounds louder than normal
  • Vehicle shakes at idle
  • Increased fuel consumption
  • Increased wear on engine
  • Vehicle lurches unsafely when accelerating
  • Increased harmful emissions

Causes of High Idle

Faulty Idle Air Control Valve

Many vehicles employ idle air control (IAC) valves to maintain idle. Your engine’s idle air control valve is the bypass responsible for keeping your engine at the proper speed while the vehicle is stopped.

There are a few different reasons that could cause an IAC valve to malfunction. Fuses and other electrical systems within your vehicle can wear out and break, leaving the valve without the ability to control itself properly. The valve itself can also fail physically, and allow too much air to enter the motor, which can cause a high idling speed. 

Vacuum Leaks

Any leak between the mass airflow sensor and the engine that allows excess air into the closed system is called a vacuum leak. Even the smallest vacuum leaks can throw off the air-fuel ratio within your engine and cause a high idle. 

In most cases having the component repaired or replaced will fix the issue and can help the engine run normally again. 

Faulty/Stuck Throttle Body

A mechanical throttle body controls the power of the engine by letting in the proper amount of air as you press farther down. When this mechanism encounters debris buildup or any kind of mechanic failure, it can allow either too much or too little air to enter the engine and cause a high idle. As your engine struggles to keep up with the lack or surplus of air, it won’t be able to run optimally. 

Throttle body detached from engine
KY Liberty, CC BY-SA 2.5 https://creativecommons.org/licenses/by-sa/2.5, via Wikimedia Commons

I Have a High Idle! What Now?

If you notice your vehicle is idling high, don’t panic. You should easily be able to drive the vehicle to a trusted professional for diagnosis and repair. Driving a vehicle with a high idle for a long period of time can lead to quicker wear and tear, but it shouldn’t cause any major problems in the short term. 

Engine Diagnosis and Repair at Lake City Auto Care

The expert technicians at Lake City Auto Care in North Idaho have the expertise and equipment to diagnose and repair your vehicle properly! Don’t let a high idle drain your fuel and wear out your engine, our friendly service advisors will walk you through every step of the service process so you know exactly what’s being done to your vehicle. Call or schedule online with us today!

North Idaho's Best Warranty

We stand behind our work 100%. That's why we offer a five-year, 50,000-mile warranty on all services and repairs. You can rest assured that when you bring your vehicle to us, we've got you covered no matter what happens down the road.

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