[divezic]

To give you a data point on O2 sensor operation, here's an interesting mix for you:

I bought a 1969 911E with a 1979 3.0 liter engine and a 1980 fuel injection. It took me a few weeks to sort out what I have but this is what I noticed...

-There is no 15 degree switch on the right valve chain cover. Since it's a '79 engine, the cover was never tapped for the temp sensor.
-The O2 sensor wire is disconnected because without the 15 degree switch the O2 sensor is worthless. Since there is no 15 degree switch then there is always zero volts to the lamba brain. The brain would always think the engine was cold and always try to richen the mixture.
-My frequency valve is directly between the throttle body and the firewall. Not too sure if that is the standard location.
-I recently changed the plugs and they were dry and black with soot indicating a rich mixture.
-Initial start when it's cold is a bit rough but smooths out within a minute.
-It runs strong and smooth when warm.

I am going to borrow an exhaust gas analyzer and lean the mixture out some.

I plan on tapping the valve chain cover, installing the temp switch and reinstalling the O2 sensor...eventually. I want to see the difference.

Hope this helps. I don't think the O2 sensor is terribly important. If I were to use her as a daily driver, then for the sake of fuel economy I'd have the O2 sensor. But for a few hundred miles per year, I'm not too worried.