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Discussion Starter #1
Hi,
I had a membrane breather issue on e92 325i 3 litre and the engine was basically whistling,
i checked would there be any suction under the oil cap, there was hence as recommended
I replaced the valve cover, new OEM from BMW (£330).

The whistling stopped, i noticed 1.there is still still a bit of suction under the oil cap
2. my mpg started to drop while on idle or traffic lights.
I reset the adaptations (https://bimmerprofs.com/re-adaptation-engine/), I thought this might be the solution.
On the motorway i got ~34mpg which i feel happy about while creating new adaptations running around ¬60mph :).
And still there is suction under the oil cap and fuel consumption drops on idle or just traffic lights.

Just after the valve cover replacement my over 300 mile average started to go down by 1mpg every 10s or so, from 25mpg down to 15.
After the adaptations were made it decreased ¬2mpg from 34 to 32. But still I've never seen it like that before.. a fraction maybe, but not like this.

Can anyone explain this please or pehaps give me advice? Should i be looking for ccv vacuum leaks or is this oil cap suction and
dropping mpg normal and all ok? Maybe it's my new membrane flexing and adjusting? I have no idea, please advise.
 

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A little suction when removing the oil cap with the engine running is normal. It's when it's so strong you can hardly open it you have a problem. Sorry I can't advise with your mpg issue.
 

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Discussion Starter #4
I appreciate the response guys.

Hmm the thing is does your car also jitters and shakes violently when removing the oil cap?

I made a video. In here you can see integrators (correction injection time bank 1/2, 5th line) in
homogeneous mode - lambda <2 and them rapidly going up to 30%, afaik they shouldn't, and you
can hear the jittering.

https://youtu.be/70SsHoJqqsE

source for this check: https://bimmerprofs.com/crankcase-ventilation/ bottom of the page.
 

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Discussion Starter #5
Ok, I asked the guy from bimmerprofs, real proffesional after short consultation
we assumed that system is air tight however the membrane spring is too strong
hence the jittering and suction under the oil cap.
Perhaps it will adjust itself with time, for the moment it might increase the oil
consumption, though that's about it.
I think it might adjust itself with time. Valve cover is oem bmw (£330).
 
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