As I always do before wiring something complicated like a 3.2, I sat down today with Mike's DME harness, wiring diagrams and a multi-meter to become totally familiar with each and every wire.

When we first received the engine, I noticed there was no O2 sensor plug, but I thought I would find it when I went through it prior to assembly.

Nope. There's no O2 sensor plug. Not only that, but location 24 on the big DME plug (O2 sensor input to the DME) has NO pin!

There is an O2 sensor on the exhaust with nowhere to plug it in nor the facility to relay that info to the computer.

Absolutely everything else pins out. We must have the wrong harness, but what other car would even have one close to this?

Your personal experiences would be appreciated.

Euro ECU and harness? As I recall (dimly), catalytic convertors were not required in the UK until 1992, so it's possible they weren't required in all of Europe until that time. No convertor, no real reason for an O2 sensor. Just program the thing to run open-loop.

Best guess I can come up with...

Engine is a 930/21 (USA '84-'86 Carrera).

The exhaust has an O2 sensor, so the computer should accept input from an O2 sensor.

Even without the cat, which will obviously not be installed on Mike's 914 installation, the O2 sensor input is very valuable and I would like to have it.

The computer is: 911.618.111.05. Anything there?

a quick google search for "911.618" reveals that .05 must be a *very* early version of the computer ...

other than that, i'm clueless ...
Andy

Fine. Was there ever a 3.2 with no O2 sensor? I don't think so.

So what am I missing here? It must just be the wrong harness.

I don't know how an engine can come with an O2 sensor on the cat, but have no wiring for it to communicate with the DME.

You seem to have a euro harness. I don't know where all your parts came from, but it seems like a mismatch to me.

If the engine is a USA spec engine, it should work with the euro ECU and harness, but it has lower compression than the euro counterpart.

My 1987 engine is a USA spec engine and harness, and when I bought my 1984 engine/harness/ trans, I found that the 1984 was euro (no O2 sensor plug), and the trans had the cooler (std in europe). When I recieved my euro engine, someone had swapped out the exhaust (taking the cat bypass pipe and leaving a cat with an o2 sensor instead). I was glad that someone had swapped out the exhaust because when it came time to pull the exhaust as it all came off without any issues (broken studs).

I am by no means an expert, but I would want the ECU and the harness to match and the engine to match the ECU.

It may have been an oversite by the dismantler, or the ECU/harness may have been changed during that engines' life for some reason. I would have my suspicions...

Wiring in the 3.2 is a complicated procedure. You need to also matchup the sensors to the guages so the inputs make sense. I had a local race shop rearrange several of my screw ups so the thing would run. And run it does! The O2 sensor he pitched. He also pitched the sensor that sits on top where the bell housing meets the engine. He left the two side by side flywheel speed sensors. I have no heat ducts or auxillary blower fans either. Less to go wrong.

Don't need no stinkin' O2 sensor........

That's funny, I have always thought it was pretty straight forward.

All you need is both wiring diagrams and be able to read them.

I'm cool with not having an O2 sensor, but I at least want the harness to match the DME.

I'm a very competent electrician, I would simply like to know whether or not the wiring harness I have will work with the DME.

Joe, I'd like to help you out if I can.

Have you traced out ALL the wires you have in your harness? Have you matched up the harness with a particular year 1984-1989?

Have you identified your ECU?

I could look up the part number tonight if not.

I have the factory workshop manuals for Carreras and they have the wiring diagrams for all 5 years. If there is no O2 plug (and not just cut off) then you have a euro harness.

It might work out fine, but I have never removed an O2 sensor from an ECU that was designed to use one. I'm not sure what would happen when the ECU tried to go to "closed loop" and accept input from a missing O2 sensor. (run rich?, run lean?)

Most of the harnesses and ECUs should be interchangable between years, but I know later cars had things (like a shift light) that the earlier cars did not have.

Does the wiring harness have a part number? (maybe it would be listed in PET as to what year and what destination it was made for)

You might call/ e mail Steve Wong over on the B board

Engine is a 930/21 (USA 3.2 Carrera)
The part number on the DME is also USA Carrera (911.618.111.05).

The harness apprears to be Euro. There is no pin (24) on the DME plug and no wiring in the harness for an O2 sensor.

We'll be needing a US harness.

Anybody got one?