I am grateful for the continued help in my little project, gentlemen. Injuneer, the review of the data logs was really helpful.

I guess my fuel gauge isn't too accurate. I hooked up my new OTC fuel pressure gauge and it was only showing about 10 lbs. I added about six gallons of 93 octane, cranked the engine a bit, and it fired right up and idled fine. I wonder if the code 015 for the temp sensor was causing the no-start issue at all? I'm thinking probably not, but that it was responsible for the very rich running condition that I observed when this project began.

As I was hooking up the fuel pressure gauge, I found this hard, thin plastic tube coming out of the loom on the PS of the engine, near the firewall. Looks like a vacuum line of some sort?

 

Do your A/C, heat, and defrost controls work? That looks like it is PROBABLY the vacuum line for the HVAC control panel in the dash.

Engine harness from Shoebox:

1995 Z28 A4 Engine Harness

If you click on the area top/center, just to the right of the silver heat insulation tape, you will get a close up look at the HVAC line that connects to the intake manifold:

http://shbox.com/1/harness1.jpg

That line connects to the intake manifold right above the connection for the fuel pressure regulator vacuum:

http://shbox.com/1/fp_reg.jpg

Other end of the vacuum line goes to the HVAC vacuum check valve:

http://shbox.com/1/vac_check_valve.jpg

Here's the HVAC control diagram - the end of the line in your photo is probably point “G” in the diagram:

http://shbox.com/1/hvac_vacuum.jpg

I'd be lost without Rob/Shoebox’s site.

 

Okay now, that makes some sense. I have noticed that the HVAC controls do NOT work properly, as a matter of fact. It loos like the end of this line should have a rubber 90-degree boot on it? Perhaps it is not "broken," and just "disconnected" from that boot? I definitely have some vacuum line issues to sort through on this car. In the last pic I posted, you can see a metal bolt sticking up. That is actually being used as a plug for a vacuum line in the approximate area you are directing me to in some of these photos.

I wonder if someone connected it deliberately or if it did break/become disconnected and the previous owner just didn't know about it?

 

The metal bolt may be pushed into the rubber 90° boot for the HVAC connection, to prevent a vacuum leak. While poking around in that area see if ther is a vacuum line matching the one in Shoebox’s photo, that runs to the fuel pressure regulator. Hard to see way back under the cowl.

 

So the 90 degree boot on that upper manifold fitting had been plugged with the bolt, and the plastic tube going to it was just hanging out, unplugged, in the plastic wire loom. Maybe my HVAC controls will work now? We'll see.

How is the plastic line attached to the boot originally? Mine was really loose in the boot, so I used a zip tie to cinch it up until I get some really tiny hose clamps.

Why would someone have just plugged the fitting rather than fixing this?

 

I don't know how the boot was attached originally, never noticed being loose. Maybe it's not the original boot.. When reassembling it, I would put a thin coating of black RTV on the last 1/2" of the hose, enough to seal it and push it into the boot. Alternatively, go to your local auto parts store and see if they have a display of random/generic hose fittings. Might have an elbow that fits the hose and the manifold nipple better,

Can't imagine why someone would pull it apart and block the vacuum. Possibly the vacuum check valve connection broke off (not unusual) and they found it easier to plug the vacuum connection on the manifold rather than replace the vacuum check valve. With no vacuum, the flapper doors that direct the air to the dash vents and the defrost vents won't work.

 

I deleted the 90 degree boot and purchased a high quality soft vacuum line from my local speed shop. I have that line plugged directly into the intake then over to the hard line that is tied into the loom. I broke off the extra curl of hard line to make a smooth transition from the hard line to the intake. Why would someone do it? They likely didn't know what they were doing.

 

That's a good idea, eliminating the boot and slipping a soft line over the hard line!

I found the next oddball issue from the previous owner to address. It's this rocker switch on the dash. I have not followed all the wires to see where they go. I noticed a red wire went behind the fuses. Pulled on it and it just came out, like it was tucked back there but not connected to anything...and the connector end is all mangled anyway. Just seems cobbled.

Not sure what people need a rocker switch to control other than maybe fans? Neutral start safety switch?

 

You can pick up power for accessories and aftermarket items by inserting a wire with a flat spade lug into one of the two (sort of) rectangular holes in the end-of-dash panel labeled “IGN” (switched 12 V power, protected by fuse #9) and “BATT” (always-on battery power, protected by fuse #11). You can use a 1/4” flat blade terminal (spade lug) and push it into the spring clips inside the rectangular hole.

I use that method to power my aftermarket gauges and their lighting, among other things.

Looks like someone put a forked terminal on the wire instead of the 1/4” lug, clipped off one of the fork prongs and connected it to one of the power sources.

 

And I also have a couple rocker switches, one to engage the line-lock for burnouts, and the other to engage the overdrive unit on the back end of my TH400 auto trans.

 

Your gauges, switches, and wiring look really clean and professional, unlike what I've got here. Maybe that red wire was once connected to something, but when I pulled it out from behind the fuse panel, it seemed totally loose and just hanging out in space.

This car has aftermarket parts, but I don't see anything that would need a switch: headers, exhaust, larger throttle body etc. Hopefully tracing the wires will allow me to see what it is/was connected to.

 

I think your red wire tucked behind the panel was at one time pushed into one of the power sources in the panel. They just pulled it out. Does the car have fog lights? Adding the rocker switch near the headlight switch may suggest what it was used for at one time.

 

Interesting question about fog lights. When I got the car, it didn't have any installed, but I have always wondered why the spaces for them on both sides of the nosecone seem like they were cut a bit.

 

Great job this looks really good!

 

We had mild temps here today so I got the car down off the ramps and pulled it out to wash it. It felt good to remove the grime that has been collecting for literally years. The paint has suffered from neglect, but there's no going back in time, so I'll just deal with it.

I had the car idling for a while with the Actron scanner hooked up so I could use the datastream function to monitor the coolant temp. It got up to about 230 degrees before I shut it down. The scanner is telling me that the fan control relays are not coming on. I definitely don't hear the fans at all. So, that's a new thing to sort through now.