Q: Low idle and stops, sometimes stalls at idle.

asked by on

Low RPMS @ stops/idle (rpms under 650), stalled @ a red light (rpms were under 500), extremely low rpms driving fast (speeds around 40-50/rpms under 1600), & sounds ruff driving (sounds like its working very hard, it sounds like the engine is "whinning"). Trans. was rebuilt 1 year ago & rechecked 40+ days ago. Oil change every 3000- 4000 miles. Throttle body & Idle control valve are clean. No codes have shown. Ideas on what could be wrong etc?

My car has 190000 miles.
My car has an automatic transmission.

As you know, 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. As this valve is controlled by the vehicle’s computer, it 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. When the engine RPM drops below the normal range of 750-800 RPM (for most cars), this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. You can test the functionality of the valve by checking its electrical resistance if you have access to an ohm meter. To do this, disconnect the IAC valve, connect an ohmmeter to pins 2 and 3 of the valve. If you get a resistance value between 10-14 ohms, it indicates IAC valve is working as it should. Next, connect the ohmmeter to pins 1 and 2. If you do not get a resistance value between 10-14 ohms, the IAC valve may need to be replaced. 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 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. Low idle and stops, sometimes stalls at idle.

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: car cutting out in low gears on stopping, traffic lights and junctions

Hello. This is often times a sign of a failing mass air flow sensor. As you may know, this is a unit that monitors the air flow into the intake as it is mixed with the fuel prior to being...

Q: Rear Driver side axle bearing

On the Grand Marquis, the front wheel bearings are of the 'hub & bearing' type. The entire hub is replaced. With the rear bearings, the axles must be removed to remove and replace the wheel bearings. Hope this helps. ...

Q: Car has rough idle and ticks.

If the engine has low compression on one cylinder it is usually an indication of a damaged valve seat or possibly a bad head gasket. If it is also accompanied by a ticking noise then there may be an issue...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...