5 Symptoms of a Bad Idle Air Control Valve in Your Car


When the engine is running but the vehicle is not moving, this means the engine is idle. During this time, the number of revolutions per minute inside the engine will change. The idle air control valve is responsible for managing the engine idle speed. The valve is a major management component of the engine which will either decrease or increase the number of revolutions per minute, depending on what the current operating conditions call for. The valve is connected to the throttle body next to the intake manifold. The engine control unit is what manages the function of the valve. Based on the information it receives like engine load and temperature, it will change the speed of the idle accordingly.

Top 5 Failure Symptoms

When you have a bad idle air control valve in your car, there are several problems and symptoms that will present themselves. If you don’t get the valve replaced immediately, your car will become undrivable. Below are the top 5 symptoms of a bad idle air control valve which you will easily notice.

1. Intermittent Idle Speed – Since the idle air control valve is supposed to manage the idle speed of the engine, a bad valve will certainly throw that out of whack. It will cause the idle speed to randomly fluctuate to different speeds rather than stay at one constant speed. The idle speed may be too high at one moment and then too low at other moments. You will clearly notice this idle speed changing by simply looking at the tachometer on the dashboard.

Read also: 5 Symptoms of a Bad Crankshaft Position Sensor in Your Car

2. Check Engine Warning Light – Whenever there is the smallest problem or issue with anything connected to the engine, it will cause the central computer to activate the check engine warning light on the dashboard. A bad idle air control valve could certainly be one reason for this to happen. If the number of revolutions per minute seems peculiar to the engine control unit, it will let you know by activating the warning light. Of course, there could be a whole list of other reasons for the warning light to come on too. In any case, you should take your vehicle to the auto shop to get it checked out at once.

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  1. Victor Fowler 2 February, 2019 at 15:06 Reply

    It’s exactly what this article addresses, cars may be different in many ways but they all still work on the same basic principals. Replacing the IAC valve is easy and if your not sure simply go on YouTube and you’re sure to find someone who has made an instructional video on how to do it. It’s how I just replaced the clutch in my car, and successfully to I might add without ever having done one before. All for less than 1/10th of what a shop would have charged me thanks to ebay where I got the entire O.E.M. clutch kit FOR $60. So order that part and retrive the knowledge you will need and as a by-product of such your accomplishment will garner you some confidence, and good luck to you sir.

  2. bennie 13 February, 2019 at 21:22 Reply

    my 01 ford focus 2.0 I can undo the battery and re kook it to make the iac valve work but after about 20 miles it dose it aging could the iac valve have a short in it

    • Roro 11 March, 2019 at 06:59 Reply

      I have a 2003 Ford Ranger and this happens to me too. My idle will randomly get low, and get to below 500 like the engine will stall. So I turn engine off and unhook the neg. battery cable & re-hook it, then restart and do idle relearn procedure…and it idles good again. But then after a few hundred miles it will start to idle low again. I replaced my IAC valve 20,000 miles ago w/ OEM Motorcraft. Maybe my truck would do better with an aftermarket IAC valve…I’m so confused about this issue. Any advice appreciated.

  3. JOSE MANUEL VEGA 19 February, 2019 at 23:51 Reply

    I have a Toyota Sienna 2001. I would like to know why or how IAC valve affects the brake booster in my car. I had the booster replaced two weeks ago, but the brake pedal seems to get hard and doesn’t brake correctly. Thank you for your help.

  4. Chrystie Galbari 7 March, 2019 at 01:38 Reply

    I had a bad AIC valve. I changed it & not the car will not start at all! What could be the problem

  5. alec 11 March, 2019 at 23:48 Reply

    I have a 2012 ford escape and at idle my car almost stalled, rpm went way below 500, but then picked back up. I think it is spark plugs needs to be changes but could it be AIC valve?

  6. Bulisa 17 April, 2019 at 15:53 Reply

    Hi my vw tenacity 1,4i the car doesnt move whn it is cold if i try to rev t it gives me a low idle till the tempreture rises service is up to date wht could be the problem

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