Unconnected / capped vacuum line 1.6 THP DS3

[utdminiman]

Hi all,

Car's been in the garage for what feels like an eternity and I've had a look under the bonnet yesterday and noticed and noticed what I think is a vacuum line from the solenoid is not connected to anything. From memory I think it was capped when I've played about with it before but it's uncapped in the engine bay at the moment.

I'm pretty sure it's number 20 in the diagram attached but can't really tell from that if it's capped or if it's meant to connect to somewhere, I think it used to 'hide' in the rocker cover but was capped?

Any body got any idea where it's meant to go or if it is meant to be capped rather than open?

I'll try get a picture of the actual line in the car later but it's currently bucketing it down with rain, so will wait a sec.

[xantia_v6]

That is the atmospheric port of the boost control valve. The thing on the end is a dust filter with a rubber body, a foam filter and a rubber cap.
There should be gaps between the body and the cap to allow air to enter the filter.
The original design was rubbish and over time the cap would shrink, restricting the air flow. This causes unstable turbo boost and causes engine fault codes on acceleration. I removed the cap on mine, leaving the body and filter.

[utdminiman]

That is the atmospheric port of the boost control valve. The thing on the end is a dust filter with a rubber body, a foam filter and a rubber cap.
There should be gaps between the body and the cap to allow air to enter the filter.
The original design was rubbish and over time the cap would shrink, restricting the air flow. This causes unstable turbo boost and causes engine fault codes on acceleration. I removed the cap on mine, leaving the body and filter.

Ah that makes sense then, the cap on mine is uncovered already so I'll try to keep it in a spot with some nice airflow then. Thanks for the help!