Edmunds Answers

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  • avatar karjunkie 12/04/08 7:58 am PST

    The idle air control valve does not make any noise when malfunctioning. Open the hood at idle and listen for a bad belt or pulley especially around the power steering pump, radiator fan, water pump or A/C compressor. It is most likely one of these that is producing that howling sound.

Answers

  • karjunkie 12/04/08 7:58 am PST

    The idle air control valve does not make any noise when malfunctioning. Open the hood at idle and listen for a bad belt or pulley especially around the power steering pump, radiator fan, water pump or A/C compressor. It is most likely one of these that is producing that howling sound.

  • snookered 12/04/08 11:18 am PST

    Karjunkie, thank you for your response. I have listened to the engine while cold and warm. When it is warmer I hear the noise and kind of builds as the engine get hotter.
    It's hard to determine the exact location of the noise. However, since the IAC valve can be eliminated, I suspect the DPFE sensor. one the sensors mounting screws is missing and is loose. Does this sensor make this noise when malfunction? I'm not sure if I have the ability to accurately check voltage.
    Thank you,

  • karjunkie 12/04/08 1:31 pm PST

    DPFE sensor failure is a fairly common problem. The symptoms are a "stumble" and what feels like an erratic loss of power when cruising around at partial throttle. However, the DPFE sensor really wouldn't make the noise you describe. You might hear a suction noise from a leaking vacuum hose going into the sensor, but no "howling". Do you have any syptoms of the car not functioning properly? Hard to turn, overheating, etc? This might give you a clue to the item that is howling. One other thing to do is remove the air filter and see if the sound comes from that area. If so, something may be loose in the throttle body area. It could even be the IAC valve! Check that and let me know. We'll take it from there.

  • subearu 12/04/08 7:34 pm PST

    FWIW, the IAC used on 2.5L Duratec motors (Ford and Mazda use) does make a fog horn noise when it isn't working right anymore. I would still suspect the IAC. One way to tell is listen exactly where the noise is coming from when it happens and find the IAC to tell if the noise is coming from it or something else. I know this isn't the 4.0L described in the question, but it may be a similar part.

    -Brian

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