Q: Car idle really low, below 250 rpm.

asked by on

October 2017 my car doesn't start, so I suspect my alternator or battery is bad. fast forward to Jan 2018, I replace my battery and my car starts. But immediately I notice that it idles extremely low. and stalls out on me. I get a diagnostic report on it and it shows that my Air to fuel sensor is bad. So I replace that. Car still idles low. My mechanic noticed I had a leak in my engine, and fixes the gasket leak. Car still idles low. He then checks the posioning of my throttle, and cleans it and the sensor. Car now will start and idle at 750 rpm, drop down to 500 rpm, and as soon as I start driving drops back dow to under 250 rpm, then stalls. What in the world is wrong with this car please help. Im thinking something related to My IAC valve, but i dont want to spend 275 on that and still have idle problems. I really need concrete assistance please.

My car has 182000 miles.
My car has an automatic transmission.

It sounds like you may have a dirty or failing idle air control valve causing your engine idle to fluctuate. The idle air control valve is a small valve on the engine’s intake system that reads the air intake as it comes into the motor. This is controlled by the car’s ECM which uses this information to make adjustments to the air/fuel ratio depending on various inputs such as outside air temperature, intake air temperature, load and various other things. As you accelerate, your car’s engine is receiving a much higher dose of fuel than when at idle and conversely, when you let off the gas pedal, there is a sudden change in this fuel supply as a result of your foot letting off the pedal. When this happens, the job of the idle air control valve is to bring this deceleration down to a slow and smooth idle rather than suddenly cutting off the fuel supply causing the motor to die. When the idle air control valve is not working properly, this cause a disruption in this process resulting in the engine not being able to idle properly. I would recommend having a professional come to your location to diagnose and inspect your vehicle.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Car idle really low, below 250 rpm.

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 front speakers don't work. Not sure if they are broken, if there is a short, or if they are unplugged.

Hi there. Check the speaker wires under the dash and see if they are disabled or detached. If the wiring is good and connected to the speakers, then check the settings on the radio and see if the front speakers...

Q: Q: oxygen sensor

Hi Destiny. Thanks for the follow-up question. A V6 engine has (4) total O2 sensors, Bank One sensor 1, Bank 2 sensor 1, Bank One sensor 2, Bank 2 sensor 2. Bank 1 and Bank 2 refer to different sides...

Q: Maintenance light - 2003 Honda Pilot

Hi there. There are numerous reasons this could be happening. The most likely reason a light may come on is that it is due for oil change. If you can, check your mileage since your last oil change and determine...

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...
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...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...