Skip the auto shop - Our mechanics make house calls

Q: My engine idles heavy 1/3 of the time

asked by on

My car normally idles (when stopped at a light) at about 600 RPM. However, about one third of the time, it will rev up to 900 or 1,000 RPM and try to lurch forward. The check engine light does not come on when this happens. My car has 120,000 miles. What could be the cause?

A: If the throttle is sticking open or the idl...

If the throttle is sticking open or the idle air control valve is sticking open, would account for the check engine light not coming on. The vehicle would have to be checked to make sure the throttle is not being held open manually by the floor mat or by other means before looking at the idle air control valve to see if it is sticking. If the valve is stuck and you disconnected the electrical connector and it still does not lower then the valve is binding and would need to be replaced. This problem would need to be seen in person by a mechanic to diagnose it, and I recommend you have it looked at before it gets worse or causes more problems. If you need assistance with this, have a certified mechanic, such as one from YourMechanic, inspect your car’s idling issue and make the necessary repairs for you.

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!

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: Manual clutch not giving much resistance

Hello. If the manual clutch does not have very much resistance and you are having trouble shifting into First Gear and Reverse, the clutch master cylinder and slave cylinder need to be replaced. These components work together to allow the...

Q: Transmission slipping not shifting (washer pump stopped at same time).

Hi there. If the transmission is shifting into 1st gear and 2nd gear, then it is not slipping. The transmission shift pack solenoid 'B' has failed and only the 1st and 2nd gears work. The 3rd and 4th gear needs...

Q: P0446 Emission control system vent circuit malfunction

Hello! We will be happy to assist you. It may be the gas cap because one way the EVAP system tests itself is by monitoring the pressure inside to fuel tank and comparing it to atmospheric conditions. If the pressure...

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...