Skip the auto shop - Our mechanics make house calls

Q: Rough idle and flickering lights.

asked by on

What is causing my car to run rough while in idle and my lights are flickering. Any suggestions? It is a 5 speed with quite a bit of miles.

This may be related to 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. 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. The lower idle may also cause the lights to dim in the event that the battery may be weak. As the RPM’s dip, the production of the alternator dos as well, causing the charging amperage to the battery to drop. 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?

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!
  1. Home
  2. Questions
  3. Rough idle and flickering lights.

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: Rattling sound coming from front drivers side wheel well.

A rattling noise in that area can be a number of things including bad struts, timing chain issue, or bent suspension components. You should have the front suspension sway bar bushings or link arms inspected for loose or worn components...

Q: Won't start, weak charge light, and is battery fully charged.

Hi there. The issue is with your battery. The battery may have the voltage, but the amperage is very low and causing the electrical system to not function properly. I recommend replacing your battery. If you need further assistance with...

Q: SUV not accelerating like it should.

The SUV is not performing well when the gas pedal is pushed. It takes a while to get up to speed and has a knocking sound when accelerating, in addition to when it is idling. From past experience with this...

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...
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.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.