paalw

I have removed the intake to try to find the reason for my high idle when warm(1150rpm warm. ok at 850rpm when starting, cold. No hunting at all, very stable both when cold and warm), and hard gearing on my S3. I already saw before I removed the intake that there were some "home made" solutions, I could see that the vacuum line from the TB that was supposed to go into the 7 way splitter, was just plugged with a screw.

So now I have removed a lot of stuff, and I am able to see what is going on (note; see, not understand). So if anyone can help me try to understand what is going on here, and what I need to correct, I would be very thankful for that. I made a thread about my intake job, but I think this vacuum sorting needs a thread of its own.

Starting with the line that is plugged, the top one on the TB. Plugged:



Then the bottom one from the TB goes into the 7 way splitter (thats wrong isn't it? supposed to be the top one?). A better view of the splitter:



Then there are only 4 other lines that are connected to the splitter. Is that aftermarket splitter or original btw? Those 4 are, seen from the end that has a connection:

1 left, empty

2 left, goes to the back of this, er, fuel thing:



3 left, goes up to and along the firewall and disappears down the PS fender:



1 right, goes to the fuel thing (pressure regulator?) in front of engine:



2 right, empty

3 right, goes down to the torque tube area, probably to transmission? No photo of that one.



Then there are some other vacuum lines that I don't know if are correct, but might well be:

1. From the front item that is attached to the cross brace, there is a line going back all the way to the drivers side fuel thing in the rear of the engine. Correct?:

From:


to:


2. From front of TB there is a line going to the PS side air valve. Correct?:




Well lets start with that and see if anyone understands what is going on here. There are some more lines in the brake master area going into brake stuff mostly, a 4 way splitter that looks kind of home made, but let's maybe take that one afterwards...

Please help

davek9

Your questions were already answered in another thread that you posted about the same things.

paalw

Dave, I assume you are talking about this thread; https://rennlist.com/forums/928-foru...n-1986-s3.html

You're kind of right, and thanks for your inputs there, really appreciated. The purpose of this thread(probably should've continued the last thread but actually forgot I made a separate thread about it) was to see if someone could see what was going on here after a lot more is revealed, if the previous mechanics did some modifications or if they really didn't know at all what they were doing.

For example, my last photo, isn't that vacuum line going onto the idle adjustment screw?? At least I think I have seen in another thread that that's where the adjuster is located. To the air valve... Looks really strange to me.

Another thing. I am trying to figure out this drawing. Is it something wrong with it? Or is it me? The view seems to be from drivers(lhd) front fender/headlight angle. But then the TPS is on the other side on my car.

bureau13

Have you seen the diagram on post #62 here? I think this shows everything you're talking about....it's the same diagram I used when I was sorting this out I think...

monkez

Dude, I feel your pain. I've had my 85 for two years and I'm still hunting potential vac leaks. When you first pull those plenums apart, it's intimidating! A couple of thoughts:

- don't go cheap in replacing the lines. Buy the original white plastic lines. By the legit rubber elbows, and for god's sake buy a new 7 way splitter. Sure there are ways around it, but just do it right.

- Trace the vac line for the transmission. reaching the metal line is a major PITA. You're likely better off running a new silicone line all the way to the transmission on the drivers' side to the car. More importantly, make sure that the line is fully attached to the transmission and holds vacuum. to get there, you need to loosen the exhaust pipes and remove the heat plates to get to where the line connects to the transmission. Once all lines on the 7 way splitter are connected, make sure they hold vacuum and move on. The rubber elbow on the computer under the passenger foot well can also be leaking as well. Also, every rubber hose, rubber seal and gasket on or connected to the throttle body is a leak waiting to happen. This includes oil breather hoses, lines that go to the brake booster and even the gasket on the oil dipstick. True story, when I did a smoke test, I found a leak coming out of the freaking dipstick. I don't think that was one of the main problems, but it's the little things that can add up.

- Buy new rubber hoses for the intakes and plenums. If you still have the ones from when you bought the car, they should be replaced.

- Check the ISV. make sure it moves well when given a current. When its closed, make sure it is restricting air flow. I just discovered that the *new* ISV I installed 18 months ago doesn't restrict jack s***.

- lastly, tackle this patiently and create a checklist. Every time you pull this apart and do open heart surgery, there's the potential for new air-leaks.

Good luck bud! If you stick with it, you will get there.

paalw

Thanks bureau13, that is just brilliant. So much easier to see where things are supposed to go. I now see that almost everything was wrong the way it was in my car, I'm amazed that it idled at all... I have 2 questions regarding the system;

1. What is no 13 in the drawing? Anyone have a photo of it? And a part number? I think it might be missing in my car. Or, it's there but I don't know what to look for.
2. Where does E and F go? One of them I guess is to transmission? Whats the other one?



Is there any chance that there is such a drawing of the other vacuum system, coming from the brake booster? I suspect there is a lot wrong there too in my car, for example this 4 way splitter? (EDIT: I see it is factory, but wrongly routed):

paalw

Thanks, it is starting to look a little brighter now. The drawing that was linked to gave me hope I think its possible to make this right, even for me I have ordered new lines, new rubber, new o-rings for the TB, and MAF, new 7-way ++

Hey_Allen

I believe that #3 is a thermal vacuum switch, screwed into the head near the back of the engine, from another discussion that I saw recently.

monkez

E & F go to the EZK and the transmission.

The EZK is in the passenger foot well. There is likely a hard, nylon vacuum line that is floating around the back of the engine area on the passenger side. When you remove the cover in the foot well, you will see where the vacuum line goes.

The transmission line is a bit of a challenge. The rubber connecting to the metal tube is likely cracked. There is a rubber hose in the engine well near the crank sensor that attaches to a metal tube. the metal tube runs down the center, underneath, but above the heat shield. Near the transmission, another rubber line connects to the metal tube and attaches to the transmission on the drivers side. If it's leaking vacuum, i recommend getting a silicone hose and run it down on the various lines on the drivers side of the car underneath. That's much easier than trying to pull the metal line and connecting to that.

928S MN

This diagram might help somewhat.

paalw

I assume you mean #13. Could it be this one with the red connection piece? Am I missing one of the connections?

nosnow

paalw

Thanks. Will order a new one.

I think last pieces to complete my order list is the 4-way splitter at the brake booster vacuum. And the mounting bracket for the fuel cooler as you see is missing. Anyone have the part number for these two parts? Can't seem to find any of them in PET.

Attachment 1349248

DeWolf

The hose going from the throttle body to that 4way is wrong. On mine, and the last 4 S3's I've had, should have a 2 way splitter off of that one way vacuum valve. That valve gets its vacuum from the brake booster hose and it supplies vacuum to the HVAC and to the vacuum reservoir. I replaced all my T's with brass ones and replace all the lines with silicone. I've done a vacuum and smoke test and not a single leak. I can go out to the car after 5 days of not running, turn the ignition and hear the HVAC controls operate. I'll add that I also replaced that one way vacuum valve with an alloy valve.

DeWolf

In fact the port on the throttle body that hose is connected to is for the front fuel damper