what does this do?

[olds_kool]

trying to figure out an intermittant starting problem and poor performance on my 2.5 tdi and came accross this

it seems to be a vacuum operated choke between intercooler and inlet manifold, vacuum pipe connects to something under power steering resevoir cover, replaced vacuum hose as it had a split, but it never seems to operate, thought it might be a cold start choke so attached vacuum gauge before starting from cold but nothing there

anyone got any idea what its for? do diesels need a choke for cold starts? first diesel ive owned so still learning !

 

[me8cat]

This vaccum unit works intake manifold flap which only works when switching OFF
engine. Operates flap which cuts off air to engine so engine stops smoothly. Opens again 2-3 seconds after engine has stopped.