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      02-06-2013, 07:05 PM   #6
mmilkov
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Drives: 2008 BMW 135i
Join Date: May 2011
Location: Los Angeles

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The boost (intake pressure) reported by AccessPort is about -8.5 psi while the engine is idling. Does someone know if this is the expected reading or does it indicate insufficient vacuum?

My gut feeling is that I may have a vacuum leak and poor vacuum will prevent the wastegate from closing. I am thinking of pulling the vacuum hose off the wastegate and measuring the vacuum with a gauge while the engine is idling. Any idea what reading I should get? For that matter, since all vacuum lines are interconnected, can I measure it at any other place, such as the vacuum line to the exhaust butterfly valve, for example?

The reason I supect a vacuum leak is because the exhaust flap (which is vacuum controlled) appears to be acting strangely. The flap is open when the engine is off (I suspect this is normal), then it closes for the first few minutes while the engine is warming up, and then it opens again when the idle speed goes down. Does yours do that, too? I though the exhaust flap should open only above 3000 rpm?
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