Brambleworth

Starting my renovation and cataloging problems. Found this vac line plugged with a screw on the passenger side of the air filter box. Disappears down behind the back of the engine. Trany maybe? Car doesn’t kick down well.

1989 Euro 928S4

FredR

Such a line is connected to the underside of the sub manifold just down stream of the throttle butterfly. What it is there for I am not entirely such - I tend to assume it is there to suck out oil that invariably accumulates there on a stock motor but I do not know that for a fact.

Whether or not what you picture is such connection remains to be seen but I suspect it will be.

linderpat

I've never heard of this nor seen it. Is what you refer to a RoW thing?

FredR

Ed,

Simple answer - dunno!

My 90S4 and GTS inlet manifold have a nipple on the under side of the throttle body casing with a nylon tube and a bung/cap type of thing routed to the rear of the engine - the OP's pic is not the std kit stuffed into the end of the tube.
It's purpose remains to be seen- I figured it would permit evacuation of any oil trapped in the low point and if that proves to be the case then obiovusly Porsche would have known they were going to get a shed load of oil in there [as the later models do]. If so it would suggest they knew full well that they had designed a crock breather wise. I would be fascinated to hear if anyone has a more sensible suggestion.

Mrmerlin

To figure this out you’re gonna need to remove the air cleaner,
Please take a picture a little bit further away of the passenger side cylinder cover,
and the backside of the intake manifold getting down to where the MAF is,
also take a picture of the heater control valve

A hard shift on the transmission is usually due to a vacuum leak,
the transmission feed is from the seven way splitter,
so that will be noticeable when you remove the air cleaner,
then you can test at the modulator and see if you’re getting vacuum with the engine running

Taguid

To make an area guess. Either heater valve or carbon canister vacuum connection.

Bertrand Daoust

+1.

Zirconocene

Is that not the connection that goes to the air pump assembly? I could swear that's what was right there on my S4 (though also disconnected). My memory sucks these days though, about on par with my actual "expertise", so follow the advice of actual experts on here.

Good luck

Mrmerlin

with the air cleaner removed and a few pictures no guessing will be required.

Koenig-Specials 928

I say it is this one that went to the Diverter Valve

Brambleworth

Will pull the filter box tonight and take a look. Thanks everyone. Also are the vac lines glued to the tees or just pushed together? If memory serves I believe nothing is hooked up to the air filter that is mounted behind the radiator, so maybe that system was removed and the vac line in question had to be plugged.

Rob Edwards

To me it looks like the line to the air pump diverter valve, which looks like it has been removed on this car.

Zirconocene

The lines are just pushed into the tees. They can still be a little jammed up but wiggling will get them out.

Cheers

Brambleworth

Turns out it wasn’t connected at either end, just stuck behind engine. Will have to look for an open port.

Mrmerlin

like I said,
if you will PLEASE remove the air cleaner and take pictures and post them,
we wont have to guess.