Low vacum and idle issue
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This is a discussion on Low vacum and idle issue within the General Maintenance, Troubleshooting & Accidents. forums, part of the Tech & Modifying & General Repairs category; Hello, When my car starts it idles high almost 1500 and the vacum is around -12 to -14 on my ...

  1. #1
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    Low vacum and idle issue

    Hello,
    When my car starts it idles high almost 1500 and the vacum is around -12 to -14 on my boost gauge.
    Also my A/R seem to go from 14.7 (normal) to 17.x, when the car goes to 16-17 to 1 thats when it start to shake and almost stall. My lights also dim when it does this.
    Once the car warms up it gets a little better.
    I'm just worred because low vacum means motor damage.
    Mods:
    STI injecters
    Utec
    vf23 turbo
    catless exhaust with uppipe

    Any ideas?

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  3. #2
    Moderator GV27's Avatar
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    Air leak. Maybe a cracked intake or vacuum hose or loose clamp or something? That's a pretty common cause of more air coming into the system than is being registered by the flow sensor. It's like having the throttle open a bit wider, but the computer is seeing closed throttle and little air flow and injects very little fuel based on that. That causes an extra-lean condition like you're seeing. I think the system is set to run a bit lean while the motor is cold for emissions purposes, so it would get a bit better once the car gets warm. My first guess would be the hose between the IC and the throttle body or a vacuum hose where something non-stock has been spliced in. From there it's anyone's guess.

    Lights probably just dim due to the alternator running too slow.

    C
    Last edited by GV27; 01-25-2005 at 09:02 AM.
    "Inasmuch as ye have done it to one of the least of these my brethren, ye have done it to me." -Jesus

    1990 Alfa Romeo Spider Veloce
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  4. #3
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    I will check for a leak.
    I just removed my cold air intake hoping it would solve the problem but it didn't
    I also reset the computer.
    Could I try cleaning the MAF?

  5. #4
    Moderator GV27's Avatar
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    It would certainly be worth a try. Be very careful with it, though.
    "Inasmuch as ye have done it to one of the least of these my brethren, ye have done it to me." -Jesus

    1990 Alfa Romeo Spider Veloce
    1992 Toyota 4Runner SR5 3.Slow
    1993 Honda CBR600F2
    2002 WRX SportWagon *sold*

  6. #5
    Administrator Trainrex's Avatar
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    Do you hear any vacuum leaks? Any strange whistling?

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    I removed my utec and the problem went away.
    I think I need to add some feul in the lower rpm range.
    The car still ran 20PSI before I removed the utec.
    With The utec gone I can't really go WOT because the stock ecu will run to much timing.
    I'm going to fix it this weekend.
    Also, my vacum went from 14-16 to 18-19 after removing the Utec.
    Thanks for the help.

  8. #7
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    normal?

    is this only when you start the car cold? because it will idle around 1500 rpms just to get the car warmed up quicker, and the higher your rmp idling the lower your vacume will be.
    but if its doing it on a warm start and staying like that i dont know, maybe it has something to do with the throatal body or something.

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