rough idle with oil filler cap off

[wvboxst3r]

I have been reading about the AOS and the white smoke. My car is new to me and I have seen the puff.

So I just was out pulling radio and did the pressure test on cap. It was a little tight to start twisting but not much pressure. But the idle got rough and tried to smooth out, heard a vacuum like noise. Again very little suction but idle changed and heard air.

Is this normal.

[san rensho]

Yes, it should run rough with the cap off since there is now a vacuum leak in the intake system.

To check the AOS, put your hand over the opening to seal it. You should feel just the slightest amount of vacuum.

[Flavor 987S]

If you run with the cap off long enough, it will throw a CEL, too.

[wvboxst3r]

Ok, I did not hold hand on but will do that in next couple of days. But from feeling of cap there will be very little. I thought that was normal with idle. New to Porsche so just being over careful.

Thanks