Q: My car idles rough when I have my foot on the brake at a stop light

asked by on

Rough idle with foot on brake at stop light or just sitting in park in driveway runs good while driving

My car has 128000 miles.
My car has an automatic transmission.

This may be a sign of a failing idle air control valve. The idle air control valve is located on or near your intake manifold that monitors the air intake as it is mixed with fuel prior to being injected into the engine. 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. However, when the engine RPM drops below the normal range of 800 RPM (for most cars), it is more than likely that you are dealing with an IAC valve problem. In cases where this valve is clogged or is failing, your vehicle will stall instead of slowing to an idle after the release of the throttle. I would recommend having an expert, such as one from YourMechanic, come to your home to replace your idle air control valve.

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

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!
  1. Home
  2. Questions
  3. My car idles rough when I have my foot on the brake at a stop light

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: Dual air control blows very hot on passenger side and warm on driver's side. Replaced the actuator with n/o change. Ideas?

Hi there. It would appear that your vehicle has a combination of problems with the HVAC (heating, ventilation, air conditioning) system. Your vehicle having dual zone climate control means there are two temperature blend door actuators. Replacing components without...

Q: Car won't crank up as well as some other electrical issues

This sounds like a BCM (body control module) malfunction. This could have been caused either by a low voltage issue or a voltage spike. If the electrical system is dead, there is a power fuse that comes from the battery...

Q: I believe my motor has been moved while installing rebuilt tranny

You may want to loosen the cross member bolts on each side and then using a pry bar shift the cross member to line up the bolt holes. You can also put in an alignment punch into the hole and...

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...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...