What does this valve do? I checked mine yesterday and saw that the vacum hose vas missing. My car is a litte sluggish around 2500-3500 rpms. Could this be the problem?

Heres a picture of the valve:

 

EGR valve, or sometimes called kombi valve, basicly, it recirculates exhaust gas into the intake during cold startup to reduce emissions and reduce the load on the cats during warm up. It alone shouldn't make your car sluggish, but the missing vacuum line and leak may be a contributing factor. Replace the vacuum line and see what happens...

Gary

 

Gary is right on the effect of the vacuum line being disconnected on your car. The valve is part of the Secondary Air Injection system and is only opened during cold starts. You may not have a CEL, you probably have some "low flow" codes.

But just a note about the valve:

I know that many call that valve a "EGR valve". It does look like one. It is designed like one. It may even be able to work like one.

BUT...

My 2.7t does NOT have a Exhaust Gas Recirculation. IF it did pass exhaust it would melt the plastic hose that is connected to it. (see http://en.wikipedia.org/wiki/Exhaust_gas_recirculation for more info on EGR.) My car uses this valve to put clean air into the exhaust to help the cats.

 

Ah ha! Thanks for the clarifications Mike! I wondered about that rubber hose, lol. Just goes to show, don't believe everything you read on the internet,

 

Most of the time is is worth every penny you spent on it. (I.E. not much.)

 

Will blocking the EGR system give a positive effect on a petrol engine?

 

My 1978 Audi 5000 had a EGR system but I think you are talking about the SECONDARY AIR INJECTION SYSTEM (SAI) in the more modern Audi's.

Blocking the AIR INJECTION SYSTEM will only effect emissions during a cold start. How much? ... I don't think much... but many governments think it is a big deal.

To answer the question you actually asked:
If a car came with an true EGR system, it is used to lower NOx emissions during normal operations. For more information, see: http://en.wikipedia.org/wiki/Exhaust_gas_recirculation

While it could be removed and blocked, it MAY require other changes to the engine. It WILL increase the pollution your car puts out.