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Unread 12-18-2013, 09:27 AM   #1
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Vacuum Question

Curious if vacuum plus manifold pressure reading should be roughly equal to barometric pressure? Running Torque and watching realtime data I typically see a vac reading of 11-22 or so depending of course on load, with a manifold reading of 3-9 on average. I would expect that the two together should be roughly equal to barometric depending on load, and wonder if I may have a vac leak driving my gas mileage down.

Any thoughts or info are appreciated.

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Unread 12-18-2013, 04:47 PM   #2
rm2001wj
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The answer to your question is Yes. Manifold absolute pressure is pressure above zero, and manifold vacuum is pressure below atmospheric. Add the two (expressed in the same units) and you get atmospheric pressure at your location.
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Unread 12-18-2013, 05:01 PM   #3
jeepingcolorado
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Is there a beginners guide to fixing a vacuum leak? I tried searching and didnt find anything on how exactly to proceed the cel's im getting are po442 and po445
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Unread 12-18-2013, 06:18 PM   #4
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Those are evap system codes, hoses run from pcv and resonator I believe in the engine compartment, along the left side rail of the unibody to the evap canister in the left rear wheel well. Look for cracks or splitting or just replace them.
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Unread 12-18-2013, 06:43 PM   #5
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Quote:
Originally Posted by rm2001wj View Post
The answer to your question is Yes. Manifold absolute pressure is pressure above zero, and manifold vacuum is pressure below atmospheric. Add the two (expressed in the same units) and you get atmospheric pressure at your location.
Thanks rm, that's what I thought but wanted a verification.
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