Suggestions for My Current P1507...?
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This is a discussion on Suggestions for My Current P1507...? within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Got back from a week out of town, started the car, and it idled very high, sometimes above 2000rpms. After ...

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    Administrator RayfieldsWRX's Avatar
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    Suggestions for My Current P1507...?

    Got back from a week out of town, started the car, and it idled very high, sometimes above 2000rpms. After a bit of this, it threw a CEL, which I pulled as P1507. After throwing the CEL, it runs like crap; I guess that's the "fail-safe mode" that the CEL refers to.

    I researched that out, and educated myself about the Idle Air Control Valve. Pulled it off, cleaned it up with q-tips, (per Nasioc instructions), let it dry overnight, cleared the CEL, and put it on to test. Same result.

    So I'm going to pull it back off tonight and clean it with carb cleaner, and try again, but I'm starting to wonder if I'm missing something. I checked for loose vacuum lines; didn't find anything. I have a 5MT, so the references that I've seen to a "neutral switch" don't apply. Another fellow on here has said that changing a thermostat fixed his...but I don't see how this is relevant when I've just started the car cold.

    Any other thoughts? If this doesn't fix the issue I'm looking at shelling out a couple hundred bucks for a new IACV. Before doing that, I wanted to investigate all cheaper options.

    Thanks for any input!
    --Ray
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    Geriatric Ginger Mod Rogan's Avatar
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    there is a Neutral switch for the 5MT..

    there should be 2 switches on the drivers side (IIRC).. the forward-most one is the reverse, and the rearward-most one is the neutral switch..

    It should be less than $20.
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    He simply abides. SD_GR's Avatar
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    As posted check the harnesses for the gearbox. Also, repeat and expand your vacuum leak search. It could be a leak onto the intake and/or manifold etc. Making sure everything else is fine is good form for the age of car anyway, plus you're looking to mod in the future from your other post so you're not wasting effort, you'll need to know either way.

    A used IACV might be another option if it saves you over 50% (if not IMO it's not worth it since you'll have a nagging doubt that the second unit is also faulty etc. if it does not resolve the issue).
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    Administrator RayfieldsWRX's Avatar
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    Hmm, for some reason I thought someone said in a Nasioc thread that manual tranny cars didn't have to worry about the "neutral switch/IACV" connection...but I certainly don't know. Where exactly is that switch? I've never concerned myself with gearbox harness stuff.

    Yeah, the thought of a used IACV crossed my mind.
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    He simply abides. SD_GR's Avatar
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    I'm not near my car but from memory the harness is "above" the gearbox so look at an angle below the IC and see what you can find. I'd suspect a vacuum leak though.
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    He simply abides. SD_GR's Avatar
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    Behold:
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    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
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    Registered User wrx0131's Avatar
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    The problem may not necessarily be the IACV.

    I threw that code, along with my speed sensor malfunction code, and it turned out to be a bad speed sensor. The car threw the code to go into fail safe mode, since the speed sensor was messed up.

    After replacing the speed sensor and resetting the ECU my car went back to normal and never threw that CEL again.
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    Administrator RayfieldsWRX's Avatar
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    I saw a reference somewhere to a speed sensor, but hadn't given it much thought since the code happened before I ever moved the car an inch. I'll do some more reading about that, though.
    --Ray
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    He simply abides. SD_GR's Avatar
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    Quote Originally Posted by RayfieldsWRX View Post
    I saw a reference somewhere to a speed sensor, but hadn't given it much thought since the code happened before I ever moved the car an inch. I'll do some more reading about that, though.
    Also consider the throttle:

    after removing the. intake manifold.. - NASIOC

    but my money is on a vacuum leak.
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    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
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    Administrator RayfieldsWRX's Avatar
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    Okay, IACV cleaned with carb spray, lubed with WD-40, cleaned off and let sit overnight to dry out. Remounted on car this morning, and still the same thing.

    I tried one more thing...I cleared the CEL, and unplugged the IACV electrical connector. This changes the behavior: car goes immediately to CEL (P0508) and fail-safe running mode. Does this tell me anything? I'm thinking no, and that the car would do this if you unplugged a perfectly good IACV.

    I will look really hard for vac leaks this afternoon. Everything really seems plugged up well, though.

    Is it possible for me to apply voltage to the IACV and see if anything in there responds? It would be nice to test that before dropping cash to replace.
    --Ray
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    He simply abides. SD_GR's Avatar
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    Let me check and see if I can tell you which wire is which on the harness clip. Meanwhile,

    P0508 and confirming bad IAC valve - NASIOC

    EDIT: OK, I've no idea which wire is which... However, this is a solenoid we're talking about, and when actuated it should click. I'd tell you to check for resistance across the valve's terminals but it's a double coil thingy and I don't know what an open loop would mean.
    Last edited by SD_GR; 06-20-2009 at 03:07 PM.
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    The world breaks everyone and afterward many are strong in the broken places. Ernest Hemingway
    I lied. I cheated. I bribed men to cover the crimes of other men. I am an accessory to murder. But the most damning thing of all... I think I can live with it. And if I had to do it all over again - I would. Benjamin Sisko
    DISCLAIMER: Opinions expressed are the author's alone and are inherently worthless.

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