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Vacuum when i remove oil cap...!!!

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    #1

    Vacuum when i remove oil cap...!!!

    Bmw 89 m20b25...

    After i replaced head gasket and started the engine now if i remove oil cap i feel vacuum and car dies immediately.

    Is that normal? Car stopped until i resolve this issue that warries me as hell.
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    #2
    No need to worry, that's normal. It's actually a test you do when you're chasing vacuum leaks if you're having trouble with the injection system.

    The e30 crankcase runs under vacuum, and if you remove your oil cap, you've just introduced a massive vacuum leak to your injection system, which cuts out the engine. You're basically allowing a lot of air that hasn't passed through the air flow meter into the inlet manifold causing the engine to lean out.
    My e30: OEM+ with M30B35

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      #3
      Originally posted by lukeADE335i View Post
      No need to worry, that's normal. It's actually a test you do when you're chasing vacuum leaks if you're having trouble with the injection system.

      The e30 crankcase runs under vacuum, and if you remove your oil cap, you've just introduced a massive vacuum leak to your injection system, which cuts out the engine. You're basically allowing a lot of air that hasn't passed through the air flow meter into the inlet manifold causing the engine to lean out.
      That's a relief thanks

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        #4
        What are most turbo setup up doing in regards to this? The valve cover being vented to atmosphere would be the same as removing the oil cap? Just tuning around it?

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          #5
          The vacuum port on the throttle body is capped so you aren't pulling unmetered air in and killing the engine.
          Your signature picture has been removed since it contained the Photobucket "upgrade your account" image.

          Originally posted by TimKninja
          Im more afraid of this thread turning into one of those classic R3v moments, where Pizza gets delivered.

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            #6
            forgot all about that. thank ya

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              #7
              Originally posted by turbski View Post
              What are most turbo setup up doing in regards to this? The valve cover being vented to atmosphere would be the same as removing the oil cap? Just tuning around it?
              No turbo stock na engine.

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                #8
                Sorry. I asked only for my own personal knowledge. Completely neglected the reason why and how the cover is hooked to TB on NA cars. Lol prob because I've never seen a bone stock e30 which is probably the reason for the dumb question.

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                  #9
                  Originally posted by turbski View Post
                  Sorry. I asked only for my own personal knowledge. Completely neglected the reason why and how the cover is hooked to TB on NA cars. Lol prob because I've never seen a bone stock e30 which is probably the reason for the dumb question.
                  It is alright man...Thanks anyway.

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