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Thread: Waivering RPM

  1. #1
    Registered User
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    CZCC-807
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    Apr 2000
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    Santa Monica, CA US
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    Post

    No emergency, but a request for info....

    Stock '72 engine w/ stock SUs. Engine warmed. At idle, the RPM has a tendency to waiver in cycles a few hundred RPM--say 900, down to 700, then back up to 900.

    I used a tee connector and checked the fuel flow from from the fuel pump, which seems to be adequate. It SOUNDS like a problem with a carb float but I'm not sure. (carbs were overhauled about 5 years ago.).

    So I thought I would post this here as I'm sure someone with more expertise than I has experienced this in the past.

    Any suggestions for a fix?

  2. #2
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    CZCC-791
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    Jon the BIG boy: Its a common problem for Z's I'm told. They call it "hunting" for idle. I dont know the solution, but I'm sure you'll get a few responses that will help. Good luck!

    Jon: old memories get jarred sometimes, see my post dated 7/2/00 for a flash of memory from the early 80's when I owned my first two Z's. Carl

    [This message has been edited by Carl (edited 07-02-2000).]

  3. #3
    Senior Z Car Enthusiast billcapp's Avatar
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    Jun 2000
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    Odessa, FL
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    Lightbulb

    A worn distributor shaft will cause this problem. Also make sure your vacuum lines are not leaking.

  4. #4
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    Lightbulb

    Jon: Hi, saw your post about the "hunting" idle. AIR, it is a common problem for early Z's possibly caused by several different problems. As "billcap" mentioned, a worn distributor shaft could cause the problem, also a vacuum leak could be the culprit. Most times that I've seen the problem it has been worn throttle shafts in the carbs. Result is air leaks into the carbs. Unfortunately, if this is your problem, the fix is not cheep. (carb replacement or have yours rebuilt by a SU professional) If you determine that this is your problem, check into www.ZTherapy.com Scott Bruning sells awesome remanufactured SU's. I saw many sets of them at the MSA show in April & they are beautiful! Best thing though was that NOBODY that I spoke to about these carbs had a bad thing to say. Totally rave reviews.

    Good luck, & OBTW think I found the cap I was looking for! Fingers crossed!

    ------------------
    Carl Stahlnecker
    72 240Z "Bambikiller"
    HLS30-55703 11/71
    cstahlnecker@hotmail.com
    bambikiller240@altavista.com

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