is it normal for 957 V8 to stumble at idle when oil cap removed?
 

Hi Guys - I noticed on my 957 08 V8, when the oil cap is removed as the engine is idling, the engine will drop RPM and severely stumble and almost stall until the oil filling cap is replaced. No check engine light appears. Is that how they all work, or is this the sign of a PCV check valve malfunction? Anyone able to remove their oil cap and have the engine continue to run totally normal?

Thanks!

It's normal.

Did the same on my '13 VW Golf R too.

I have had other cars that did that but never tried it with my piggy. Crankcases all run pressurized these days. Maybe it helps oil foaming. Not sure what else. Its part of the emissions system too.

Thanks guys!

I have to ask what inspired you to try this?

You've opened a massive leak into the engine gas recirculation system by doing this.. that's not how the engine expects to run.

Air-Oil separator check... seeing if it acted like the 996, which it does not! That's why it concerned me as a 996 will run with the oil filler off.

At least in my case I was changing then refilling oil, wanted to get oil back in the filter before I added the last oil. Was surprised how poorly it ran.