The VANOS engine controls rpm by adjusting the valve timing rather than throttle position (air flow). The throttle plate opens fully while the engine is running. This means that there’s negligible vacuum at idle. That’s the main weakness of the CCV system.

Here’s more info:

https://www.bimmerfest.com/forums/sh...d.php?t=911135

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2005 X5 4.4i SterlingGrau, Sport Package, DSP
Build 3/12/2005