Mystery vacuum tube

Anyone know the function of this vacuum tube?  I've just replaced it ….

Think it's to do with cab idle stabilisation

That was a fast reponse!  Thanks!  This is a GTi version - not naturally aspirated - still the same?  Idle stablisation?

yeah - only found on the GTI

Is your car a cabriolet or a hatchback?

Normally only cabriolets get that vacuum sensor. I can look up a bit more 'what it does' info when I get home if you like?

Hi Ross,
Yeas - mine is a GTi cabriolet - first registered March 1985

many thanks for your help.
M

Right! Done a bit of research to refresh my memory! I traced it a couple of months ago by the wiring, where its connected etc.

Its in the Haynes manual wiring diagrams listed as 'Vacuum time switch' and its wired up to the 'switch for acceleration enrichment' which is located under the throttle body.

I'm guessing that there is enough vacuum in that pipe it actuates the time switch and that sends current up to the accelleration enrichment switch.

I know no more! Maybe its some full throttle enrichment thingy? Maybe it actually reduced the amount of air getting through the throttle body rather than increasing the amount of fuel?

Anyone know?

Cheers,

Ross

Cool - thanks Ross. That'll do it.  Essentially it is a function that enriches the fuel mixture when rapid acceleration is needed - how it works exactly is not needed to be known but I can guess - the vacuum pulls a rubber diaphram forward, causing a swith the activate which either adjusts the fuel input or the air input or both - either way the air/fuel mix goes from lean to rich giving you more punch.

Thanks for your help matie - good job all 'round.

Readers of this post should be aware that the natural lay of this hose is across the rocker cover, causing the the hose to melt through.  It is easy to replace - new hose available from VAG (357906092C) at ?2.84 and it is possble to relay it away from the rocker cover using a couple of cable ties:  securing the hose to the braided fuel hoses running to the injectors.

M