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Discussion Starter · #1 ·
What should a vaccum gauge read at idle? I'm designing some evoscan gauges, and had originally set up the vac/boost gauge to read from -30 to +30. After watching the gauge I think my car might have a vaccum leak after watching the gauge. So I'm wondering what it should be reading?
 

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just remember that vacuum is not read in PSI, it's read in in/Hg (inches of mercury) and is normally somewhere between 17-22 in/Hg. What are you getting? Are you using the car's sensors or did you hook up an actual vacuum gauge?
 

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Discussion Starter · #4 ·
yeah I know about the in/Hg. I'm using the car's factory sensor, and logging with evoscan. I'm only getting around 8-10 in/Hg. So I guess I have a vaccum leak. Any ideas on where I should start looking?
 

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What's wrong with the factory sensor/evoscan?
Without a gauge you won't know whether it's your sensor or actual low vacuum. As far as diagnosis, you listen for a Tsssssssss noise around the intake manifold while the car is running and do a real thorough inspection of all vacuum connections hooked up to the manifold. Also, the gauge will tell you if it's fluctuating at all which can help with the diagnosis
 

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Couple of more questions: Are you having any actual issues with unstable idle or the car nearly stalling (or actually stalling)? Those are prime indicators of a vacuum leak.
 

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Discussion Starter · #10 ·
Couple of more questions: Are you having any actual issues with unstable idle or the car nearly stalling (or actually stalling)? Those are prime indicators of a vacuum leak.
It has been wavering a little (very minor) lately. I originally thought it was due to the fuel trims which I had scaled the maf 2 or 3 months ago for the bigger intake. I'll go outside soon and take look at this stuff soon. Thanks for the help.
 
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