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Old 05-20-2010, 09:53 PM
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vacuum gauge needle fluctuating really fast

i have a car missing at higher rpms. the vacuum gauge is fluctuating between 18 and 12. the needle moves really fast between these two numbers. car seems to idle fine

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Old 05-20-2010, 10:14 PM
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Then it`s losing one of several possible things. Spark is falling off, fuel is falling off, valve springs are worn and have reached there limit, or camshaft has reached it`s RPM limit.
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Old 05-20-2010, 11:04 PM
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What is the gauge doing at idle?
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Old 05-21-2010, 05:06 AM
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Sounds like a broken spring or valve bounce from worn out springs. A spark issue or fuel issue will lower vacuum but not make it bounce rapidly. If you have headers and an infared gun you could find the cold cylinder and test those springs first. Fix it now before you burn a valve! Good luck.
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Old 05-21-2010, 05:54 AM
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Here's a quickie reference sheet on reading a vac gauge. http://www.centuryperformance.com/tu...e-spg-148.html
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