Skip the auto shop - Our mechanics make house calls

Q: Erratic engine idle - 2005 Dodge Dakota

asked by on

When my ac is off my engine idle is just fine. But when the ac is on the idle is very erratic. I have a feeling it's the iac valve because when I pulled it out it had a bunch of carbon on it. I cleaned it best I could and it's still the same.

My car has 129000 miles.
My car has an automatic transmission.

As you have said, this may be related to a dirty or failing idle air control valve. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle’s computer which 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. This is all controlled by the idle air control valve. When the engine RPM drops below the normal range of 750-800 RPM (for most cars), this may indicate a dirty or faulty idle air control valve.

In your case, this may be related to the valve not maintaining the proper voltage or connection in which case it may need to be replaced. I would recommend having an expert, such as one from YourMechanic, come to your location to determine whether the idle air control valve is faulty replace it if so.

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: Engine vibrates at idle

Hi there, thanks for writing in. I'd be happy to offer my insight. I'm curious as to your vehicle's motor size. There are four different motors available in your Cherokee, each with their own set of issues. I would...

Q: Headlights flash on and off

If your vehicle is experiencing intermittent problems with the headlights, there is probably some sort of electrical problem present somewhere. That particular year and model is known display symptoms such as the ones you describe, when the Central Timer Module...

Q: Engine shuts off

Hi There, It sounds like you are describing the symptoms of a failing throttle position sensor. The throttle position sensor monitors the throttle position of the throttle plate inside the throttle body in relation to your foot position on 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...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.