Q: Car seems to idle high

asked by on

Car idle high, extra loud on front passenger side - so it seems.

My car has 91000 miles.
My car has an automatic transmission.

This may be a sign of a vacuum leak. A vacuum leak can be one of the most frustrating and difficult problems to diagnose. High idle speed is a common sign and stalling is another. Confirmation of an engine vacuum leak can be a very loud hissing sound coming from the engine area. When a vacuum leak is present in an engine, this causes an excessive imbalance in the air/fuel ratio which creates a loss of power and causes the motor to run at a much higher RPM as a result of the increased oxygen present in the fuel charge being injected into the motor.

This may also be a sign of a dirty or faulty idle air control valve. The idle air control valve reads the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. Since this valve is controlled by the vehicle’s computer, it will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed. When the engine RPM drops below the normal range of about ~800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. I would recommend having an expert from YourMechanic come to your location to diagnose your running condition as these can be very difficult to trace or detect.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 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
  1. Home
  2. Questions
  3. Car seems to idle high

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: how do i locate cylinder 6 on my car

The front of the engine has the belt on it. Now looking from the front of the engine, the left side front cylinder is 1, 2, and 3, and the right side will show cylinder 4, 5, and 6. If...

Q: Q: AC blowing hot air

This is a common issue, and as a matter of fact, this has happened to me. The ac system uses electrical motors that are called actuators to move the blend doors behind the dash. These doors direct the air to...

Q: Truck dies when not on the throttle.

Hello. A few things I would check are the timing, the idle air control valve, and the condition of the vacuum hoses. Retarded ignition timing can sometimes cause low throttle issues, and can definitely cause stalling. The idle air control...

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...
How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...