oil filler cap - change in idle speed - BMW Forum - BimmerWerkz.com
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#1 (permalink) Old 09-05-2009, 02:04 PM
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oil filler cap - change in idle speed

Is it normal for the idle to change if you remove the oil filler cap while the car is idling?
I was looking for vacuum leaks or anything that would give me a clue as to why my car (1991 535 - E34) doesn't always idle so well.

When I pulled off the oil fill cap the idle got worse.

I know this car does not have a PCV Valve but there is a breather hose from the valve cover to the air intake.

Thanks.
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#2 (permalink) Old 09-06-2009, 08:04 PM
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BMW's run a sealed crankcase therefore by removing the oil cap you are creating a vacuum leak.

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#3 (permalink) Old 09-06-2009, 08:08 PM
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Good - so it is normal then - that's good news.
Thanks for the explanation Dirty Tool.
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#4 (permalink) Old 09-06-2009, 08:16 PM
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NP ... glad to help.

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