Q: Q: Engine idle fluctuates

asked by on

My car does not idle after starting in the morning or after being parked for hours. It's idles roughly with air conditioning.
My car has an automatic transmission.

You may have a dirty or failing 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. 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 and repair your idle air control valve.

Was this answer helpful?
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. Q: Engine idle fluctuates

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: Startup difficulty

Hello there, a few different things can cause an intermittent no start condition. The most likely causes are the battery, fuel pump, starter, ignition switch, battery cable or a wiring fault. You have replaced a few of these components, but...

Q: Sway arm broken

Technically, as long as the sway bar doesn't come into contact with other moving parts, or rub on other critical components, you should still be able to operate the vehicle. You will need to understand that the handling will definitely...

Q: Car idles fast when stopping.

Hi there: It looks like you've inspected all the normal suspects of a high engine idle situation. One issue that pops up occasionally; especially on early 2000 period cars, trucks and SUV's is due to a faulty radiator coolant temperature...

Related articles

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...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...