socalclimber

You know what's interesting is that for an 86 4000 CGT, all the parts places are showing a single-wire, non-heated O2 sensor. Maybe there is a split in 86/87, some cars with 1-wire and some w/ 3-wire?

I don't think it will matter that much. The heated part is for the first few minutes while exhaust and CAT heats up. They both do the same thing. If you do get one, get a Bosch.

I think I would check DPR current first (why spend the money if you don't have to?), see where you are, this will show you how O2 is behaving, or if it's even working. I'm an advocate for test first, replace second (plus you learn more anyway)!

First, replace all the vac lines, they're cheap! Is your volt-ohm meter a digital one that can read milli-amps (ammeter) scale?

Plugs, wires, cap, and rotor are in good condition, right, and Bosch?

dcsst28

Yes, the plugs, wires, cap, and rotor are all Bosch, and they all were replaced last summer (I haven't driven the car since then).

Also, I bought 10 feet of the vacuum lines you showed me. Maybe I will seal some leaks.

Yes, my multimeter is digital and handles milliamps. I will check the DPR current this weekend. I agree that testing first is better. I also have to keep in mind, though, that if I want to get any work done on the weekends, I have to order the parts at the beginning of the week so they will get there in time.

Yeah, I saw that all the oxygen sensors for the 1986 Coupe GT at the online parts stores had only a single wire. I found one for a 1987 Coupe GT with three wires.

socalclimber

I sent you a PM.

socalclimber

1-wire or 3-wire O2 sensor, either way, it's not a deal breaker. Go with what you have, and test the functioning of it with DPR accuator current, and tests in Bentley.

If you have any vac leaks, or ignition system misfires, no O2 sensor is going to make it better, 3-wire or 1-wire.

When I look on AutoHausAZ, for Audi 1986, here's what they show:

4000CS Quattro = Bosch 13957 3-wire 36" $68
4000S = Bosch 13957 3-wire 36" $68
5000S Turbo = Bosch 13957 3-wire 36" $68
5000S = Bosch 11051 1-wire $32
5000CS Quattro = Bosch 13957 3-wire 36" $68
Coupe GT = Bosch 11051 1-wire $32

My guess is that Audi uses the same FI harness for the 4000 CS and Coupe GT models that are 5-cyls (the 4000S is 4-cyl so would be different). But that is purely a guess, I don't know.

If your O2 is sluggish, and you want to replace it, you could go with the 3-wire, but it's not what your car calls for. The 3-wire shows a longer service life, 60k miles.

dcsst28

So, I tried starting the car after letting it sit for a week. After cranking for a few seconds, it started right up and idled well.

These are the wires hanging near the horns. There are three loose ones. The red wire in the background is the wire I have connected between the thermo-time switch and the starter.





I do not think the wire I am looking for is among these three, because they do not seem to reach to the starter.

I am going to check the DPR current next to see if it fluctuates, like you said, for determining if the oxygen sensor is working.

dcsst28

I am unable to measure the DPR current while the engine is running. The engine dies shortly after starting if I try starting it with the multimeter attached. If I attempt to attach the adapter and multimeter after starting the engine, the engine dies before I get it hooked up. "Limp home mode" does not seem to work very well.

I pulled the lower panel off the driver's side dash, and I found a mess of wires. It looks like someone has been there before, and they have done a lot of splicing. There is a device screwed to the bottom of the steering column, which I think was part of an alarm system at one time. There is a plug hanging freely. I have not found the six-point connector yet, but I will keep looking.

socalclimber

Post a pic of your multi-meter and where leads are plugged into meter. You have it set on amp or milli-amp scale, right? Usually you have to plug in leads to different source on meter when doing ammeter readings.

ONLY plug in test harness when engine is off. Connect ammeter on a nother circuit, like a 12v light bulb, to make sure you can read amps or milliamps.

Can't see anything in those photos really.

Terminal 15A/50 from starter to #24 OXS ECU isn't a big deal. It gives FI (DPR) some enrichment ONLY DURING cranking of engine to aid in starting. Once you let go key and engine is running, it's done. Later for that.

Focus on reading DPR with your ammeter. Feel free to email me, I'll send you my email in a PM.

Keep the faith!

dcsst28

Yes, I had the leads plugged into the wrong holes. I plugged them into the proper holes of the multimeter, and I checked the DPR current. Upon starting, the current is about 32 mA. It slowly decreased until eventually it was around 6 mA. There it fluctuated between 6 mA and almost 8 mA. I increased the rpms to about 3000, and I observed the current fluctuate between about 9 mA and 10 mA.

I will search around under the dash for wires a little longer, but I will probably end up just running a wire from the thermo-time switch to the starter. I need to get some connectors and a soldering iron, so I can connect the wire properly.

I noticed a new problem; I have a fuel leak. It seems to be coming from around the fuel pump and filter area. I will inspect it further to determine the exact location.

socalclimber

Good job! I think you got it with the DPR. You're doing it!