While trying to fix my idle problem, I noticed this. I'm pretty sure there's supposed to be a hose connected here:



What is it exactly? (I think it's a water-thermo something-or-other)
and where should the missing hose lead to/from?

I doubt it's causing my idle issue, but it should probably be fixed.

 

I believe it wraps around to the other side of the throttle body. There will be another nipple missing a hose on the front bottom of the throttle opening.

 

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thanks, guys. I'll check it out tomorrow.

What problems would this cause?

 

The outer secondary throttle plates will default to open, so you will basically have the effect of the TB mod. The actuators always fail anyway, so it's likely it wouldn't work even if you hooked it back up.

Also, if that second vac line in the picture is still connected, it goes right to the UIM. When the car warms up, and that thermovalve opens, you will get a nice big vac leak from that open plastic nipple.

 

So this could be the cause of my idle problem?

I can't find the hose anywhere. Can I just replace it with some vacuum line or do I need that check valve thing?

 

When the water is cold, there is a path from one nipple to the other to feed the double throttle diaphram. When the water is hot, there is no passage to the double throttle diaphram. So I don't see a vacuum leak when the vacuum hose and the delay valve exist. If the vacuum hose and the delay valve are missing, you could have a air leak when the water is cold. Goes away once the water is hot.

Let's say I'm wrong. So cap off that open nipple. Can't leak then.

 

Won't there still be a hole on the VDI, though?

 

Sorry if I'm intruding, but can we please clear this up? I just realized my nipple in the exact spot is not connected also. So this is a big help.

In HAILERS diagram, where does the Vacuum hose with the check valve connect to?

 

Good question.

Edit: according to RotaryRocket88 and the EGI schematic in the Haynes manual, it goes right into the upper (or possibly lower) intake manifold. However, I can't tell where exactly.

 

Nope it goes to the block, and without it you have a major vaccum leak, ill try to get some pis tomorrow

 

Ok, so the circled nipple in question connects to front of the throttle body.

On the factory vacuum diagram on my hood, it shows that hose going directly to the UIM aka Upper Intake Manifold. There are 4 vacuum nipples there and it shows the hose going to the lower nipple.

All relative to a S4 T2.

 

Ok. I got the two hose on the water thermovalve backwards, even with the jpg I attached out of the series five non turbo FSM. I'll get over it.

The aft nipple is the source of vacuum. On a SERIES FOUR it comes from a nipple directly below the water thermovalve. About six inches straight down from that plastic nipple.

The forward nipple goes to the double throttle diaphram. The vacuum on that line is only there when the water is cold in the engine. When the water gets hot, the water thermovalve shuts the gate and no vacuum is on that line anymore and that makes the outer set of throttle plates spring wide open.

I know he has a series five, but I'd bet the source of vacuum comes off the lower intake manifold as I described above.

 

Here's another pic out of the FSM. It devotes about three pages to the double throttle/ water thermovalve etc.

You can see where the hose come and go in the jpg. Although that view is for a auto car, the feed comes from the same place. See the local FSM for manual pictures etc.

 

So on the vacuum line from the plastic nipple to the double throttle diaphragm, on a manual car, you do not need the check valve correct? Thats only on an Auto? If so I messed that up when I "fixed" it last lol

 

The second to last jpg I attached, shows no checkvalve or delay valve b/t the double throttle diapharm and the nipple on the water thermovalve. It does show a check valve b/t the other water thermo nipple and the source of vacuum. See jpgs. Manual cars.

My double thorttle diaphrams are all busted and I'm a little weak on how things go as far as the vacuum lines/check valves. Pictures from the FSM should be right.

 

I'm getting really confused and wondering if we are all talking about the same car. Just to clarify, I have an S5 non-turbo manual.

younG_Gunner apparently has an S4 Turbo.

This weekend I should have time to really figure this out and clear some things up.



Here's the deal with my car:

 

Yeah my bad, still causes a vacum leak though, i had thought it was the block when i was messing with it the other day, i just ran my hand along the hose without actually looking, i didnt realize i hit any intake maniolds. I thought i was past them and on the block.

 

Turbos have the double throttle vac line connected to one of the nipples on the back of the throttle body, but the concept is the same.

As far as I know, both the S4 NA and S5 NA have the single line from the UIM to the thermovalve, then the line with the check valve going to the double throttle diaphram. Then on automatic cars, you have the extra diaphram and line in your pic.

In any event, the line going to the UIM is the key, if it's there, you better have something connected to the other nipple(s) on the thermovalve. I said it backwards earlier, like Hailers said, cold=open to vacuum & hot=closed. If the double throttle doesn't work (none I've seen work), then remove all the lines, and cap the manifold nipple.

 

According to the series five FSM, Fuel and Emissions section, a manual, non turbo should look like this attached jpg.

The Gunneys series FOUR Turbo should look just like the vacuum diagram that came off his hood. Water thermo gets fed vacuum from the bottom nipple on the back of the throttle body and goes to the water thermo. From the water thermo it continues on to the double throttle diaphragm.

 

Which is exactly how my '91 appears.
BTW...that "t" fitting below the check valve (capped off in the diagram) is where the vac hose to the cruise control actuator attaches.

In case anyone was wondering, like.

 

By the way ULTRATACO, most likely you do have a vacuum leak because the vacuum line in your picture is not the one that goes to the double throttle diaphragm so it must be the vacuum feed line. If it is, then it's on the wrong nipple and WILL cause a vacuum leak once the water gets up to temperature.

That vacuum line belongs on the fwd nipple, not the aft nipple.

Once the water is up to warm, the vacuum line will start to leak air from the filter on the water thermo valve. If you put it where it belongs that won't happen.

 

Well I looked and the nipple on the UIM is already capped off. I guess that means I don't need to mess with it anymore?
According to this pic in the FSM (pg. F1-35), mine is hooked up correctly, with the rear line going to the throttle diaphragm. The order of the lines is switched on the auto.

And just fyi, my idle problem is that my car will not idle at any temperature. I replaced the TPS with a used one, which worked great once warmed up for a few weeks, and now my car doesn't even try to idle.

 

s5 turbo 4 nipples firewall side of uim top to bottom. top fuel injector bleed (firewall side of lower intake top most nipple) next is the lower fuel injector bleed (lower intake right between the oil injectors) next runs to the gang block for the oil injectors and the bottom one connects to the hose w/ the check valve coming off the water thermovalve