Skip the auto shop - Our mechanics make house calls

Q: When my car is at idle in park or neutral the Intake Air Control Valve fluctuates, causing the RPM's to do the same.

asked by on

When my car is at idle in park or neutral the Intake Air Control Valve fluctuates, causing the RPM's to do the same ranging from 800-1200 rpm's. If I unplug the IAC valve it stays at a solid RPM. Every sensor I've used had the same activity. So the PCM is making it fluctuate, what could cause that?

My car has 240 miles.
My car has an automatic transmission.

Hi there. It sounds as though the idle air control valve (IAC) may be sticking. It is not uncommon for carbon to build up in the valve, the computer will try to overcompensate to correct the slow reaction inside the IAC, and therefore the idle will fluctuate. It would be best to observe the commands from the PCM with a scan tool if you cannot physically see if there is carbon build up. A certified professional from YourMechanic can come to your car’s location to diagnose the idling problem and assist with repairs.

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

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!
  • Home
  • Questions
  • When my car is at idle in park or neutral the Intake Air Control Valve fluctuates, causing the RPM's to do the same.

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: My sunroof won't close

Hey there. The sunroof uses a motor and a track that opens and closes the sunroof. The tracks are usually plastic and can begin to lose teeth, which does not let them operate. In cases where the sunroof fails to...

Q: P0300 codes while idling

Hello. If unplugging the MAF sensor causes the engine to run better then there is a secondary air leak into the engine. This means that there is a vacuum leak from someplace. Most of the time on this engine it...

Q: Putting new engine in a '88 Pontiac Firebird Formula

If it's an '88, it will have an orifice tube. They have always had orifice tubes. Most of the orifice tubes on GM products come off of the condenser in the front of a vehicle. The hose that comes out...

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...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...