Oil cap removed = Increase rev?

[Techen]

So, When I first got my car and since then, When I take my oil cap off it would rough idle until you put it back on and it would go back to normal....

I checked it today and once removed the car will increase it's revs up a fair bit, You can hear the induction sucking in tons of air to cope too then putting the cap back on I can only say it starts... breathing? For abit then returns to normal.

Can't say I've noticed any difference in power, Maybe MPG. My chain sounds like hell too right now, Not sure if its to do with the oil cap thingy but any ideas?

 

[pluves1]

You need a new PCV as discussed here. It will only get worse.
http://www.audi-sport.net/xf/threads/replace-pvc.260697/#post-2648329

 

[Techen]

Are you sure it's the PCV? As people complain of a rough idle when it's broken which my car does not suffer from. Its completey normal when driving, It's still powerful, Clean idle, It's only when the cap is lifted it sounds completey stuffed.

 

[pluves1]

Yep. One way to tell if the PCV is gone is to remove oil cap and the revs will increase. We had no issues with power or rough idle only that sometimes when in town traffic the revs would increase without pressing the accelerator. Your PCV isn't working as it should and a new one should also help reduce the clatter from the engine that you're experiencing as well.

 

[Techen]

Yep. One way to tell if the PCV is gone is to remove oil cap and the revs will increase. We had no issues with power or rough idle only that sometimes when in town traffic the revs would increase without pressing the accelerator. Your PCV isn't working as it should and a new one should also help reduce the clatter from the engine that you're experiencing as well.

Thanks so much Pluves, Am just going to do a PCV Revamp Delete as am remapped anyway.