O2 Issues and confusion in general

[RickM]

Well from what I've read here the US Carreras will run in open loop mode when the O2 sensor is remover. Which will default into continually running rich. I'm interested in how ROW cars handled this.

Did Canadian cars cars have ROW ECUs with O2 sensors?

[Dan Owens]

I think I'd send John Walker or Wayne an email and ask him if they know.

[Wayne 962]

It's very difficult to get proper fuel injection components here in the US for grey market cars. I believe it's actually illegal to import and sell the aftermarket Euro parts in the US market...

-Wayne

[Steve W]

As you have basically an early ROW Carrera, the ROW DMEs do not have the circuitry implemented on the board to integrate the O2 sensor into the programming - unless the DME was modified with the appropriate resistors and capacitors, and the EPROM was changed to a U.S. program that did recognize a sensor. I've seen a few ROW Carreras this way, most just have an O2 sensor jimmy rigged to go nowhere to fool federal inspection, some have been connected to a makeshift aftermarket electronics box which attempts to modulate some DME sensor input, and some have the federalization done properly by replacing the ROW DME with a US one, wiring in the O2 sensor, and installing a cat. You should figure out what you have, or you can basically be wasting your time installing an O2 sensor that doesn't do anything.

The single black wire is the sensor output to the DME, the paired white wires is the 12v preheater circuit.

By running a US Carrera with an O2 sensor disconnected, you basically are running like an ROW car. It will run a little richer with the sensor disconnected, but it will still run somewhat lean because the programming is designed so that even if the sensor failed or was disconnected, the emissions friendly stoichiometric ratio of 14.7:1 is closely maintained. However for performance, 14.7:1 is too lean, and thus ignition timing remains more conservative. A ROW Carrera by default runs somewhat richer than a U.S. car with a disconnected O2 sensor, so it can withstand greater ignition timing with the same margins.

Point is, you really do not need a working O2 sensor with the stock DME programming. It is only necessary to maintain optimum emissions levels, and if you have a catalytic converter, maintenance of the stoch ratio to keep it clean and efficient.

[laddsc]

Thanks Steve. That answered a number of my general questions about the difference in US vs. RoW cars.

The only thing I know about the DME is that it was replaced at some point. It has been written on with marker "86 Carrera" which is a year newer than my car. Obviously a used part. The part numbers on it do match the RoW part number that is correct for my car but I have no idea if it was reprogrammed. I am going to have to do some investigating.

[laddsc]

Update. I decided yesterday to uplug the O2 sensor and see what would happen. I realize this will typically mask a problem but in my search to understand the issues, I thought it was a good test. The difference was amazing. I have no more mid-range surging or hesitating and the power is far better than it was before. I was getting 25mpg previously which was a good indication I was running lean and I will test it in a week or so to see what this changed. Not finished with the investigation but the power is sure nice. More what I would have expected from this car.

[laddsc]

Another update - Ran with the sensor unplugged for a tank of gas. Still got 25mpg. Mind you, I do a lot of freeway driving but any around town and in canyons I am 4-6k all the time. It is running awesome right now as well. I am still way confused but it is tough to complain when I have great power and mpg. It is going to take some time figuring out how they supposedly made this car comply with US standards back in 85 and what they changed. At least it is running well for now.