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Thread: Engine speed jumps up

  1. #1
    MsJackson
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    Default Engine speed jumps up

    My 280z (EFI) idles at a steady 1000 rpm when at rest, when i start driving however the idle jumps up to 2100 rpm. Its stays high, until i come to a stop then it drops back down to 1000. If I am moving at all the idle is too high!! Help me please

  2. #2
    Garage Queen chickenwafer's Avatar
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    you're not idleing if your moving, so I'm affraid I don't understand what you are saying.......
    When you drive for a few minuets, and get to a stop light and come to a complete stop, how is the idle then? If you have your foot on the gas (which would cause you to move) the engine speed is going to increase- that's a given.
    Please explain a little more throughly......


    Dave
    1974 Datsun 260z manual: garage queen

  3. #3
    somewhat twisted thehelix112's Avatar
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    Is it an auto?

    Dave
    Dave Andrews

    Daily: 1973 240Z, L28ET, Autronic, GT35R.
    Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild.

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    MsJackson
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    Default Corrections!!!!

    Ok this is what i mean, when i am moving with my foot on the gas all is ok...However if i put in the clutch and its in neutral, the engine speed is at 2100 rmp. when i come to a stop the over rev drops back down to idle at 1000 rmp. So it only happens when i am moving. If i upshift when moving, the car will push until it hits 2100 rpm. So if moving the engine wants to be at 2100!! If anyone can help, it would be wonderful.

  5. #5
    Former frequent poster sblake01's Avatar
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    If you have a California car, check the altitude sensor. When they act up, they cause a problem similar to what you are describing.
    2004 Ford Ranger EDGE Supercab
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  6. #6
    of the Silver Shield Soc. dogma420's Avatar
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    fill out your profile information with where you live.
    --Dave aka Dogma420 My Gallery
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  7. #7
    EZ
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    Also look at your BCDD
    Shallow Ed's 76-280z

  8. #8
    Registered User Ken's Avatar
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    Check your throttle opener valve setting. There is an adjusting screw that does not let the throttle snap shut when you remove your foot from the accelerator pedal. This is part of the emission control system. This is mounted on the left side of the balance tube and consists of a vacuum control valve which operates the servo diaphram which in turn controls the carburetor throttle valve. If this screw is out of adjustment it will retard throttle return and result in a longer delay for the engine to return to idle speed rpm.

    This should solve the problem.
    Silver Bullet 240Z

  9. #9
    Registered User Ken's Avatar
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    Just noted you have a 280Z EFI! The info I posted is for the 240Z. I don't know if you have a similiar system function on the 280Z.
    Sorry....
    Silver Bullet 240Z

  10. #10
    Garage Queen chickenwafer's Avatar
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    you're EFI, so it could possibly be the themorstat, but I'm doubting it.
    1974 Datsun 260z manual: garage queen

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    Check the flap in the airflow meter. If it sticks it could cause your problem. A little WD40 will correct the sticking flap.

  12. #12
    of the Silver Shield Soc. dogma420's Avatar
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    How about a completely wasted distributor screwing up advance, etc...

    I had a similiar problem to yours, replaced the dist but also adjusted carbs at the same time (something you don't have an issue with)...so I'm not sure what really fixed the idle issue...
    --Dave aka Dogma420 My Gallery
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  13. #13
    Registered User 28oz's Avatar
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    Default me too...

    odd... id like an answer too. but i think its a flap problem. mine stays at 950 when im rolling (with the drivetrain disengaged). and when i come to a complete stop.. back to 800....

    but my idle also slightly moves up and down (like 25-50rpms), so i think my flap spring is loose... but i dont worry too much about it anymore... just happy to be driving the car.
    77' 280 Z

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    errrr... That's it. for now..muahahahah!

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