Hi everyone :)
First off, I want thank everyone with their advice on my tach problem.
I'll post up pics once I get back on the road.

My question is regarding the Oxygen sensor.

Doing some cleaning in the engine bay I noticed that the O2 Sensor was unplugged on my car. It's the single wire coming from before the catalyst.
Is there a reason the previous owner unplugged it? Should I plug it back in, it's running fine right now?

Thanks
:drink1:

So I did some research both online and in manuals and it seems that the fuel injection system on my 83 320i is not really adjusted by the use of the O2 sensor, is this true or did i misunderstand?

I read something to the effect, that the sensor monitors the fuel mixture and sends back the signal to the ECU, but I'm not sure if anything is actually adjusted with regards to running it leaner or richer due to current conditions, or if it is just a system to warn of possible problems with the emissions system.

I think the o2 just monitors at start up and low speed running conditions. If it is running good, and passes inspection, don't worry. if after a while it starts to run erratically, idles up and down, and shakes a bit, you might want to connect it or replace the O2 sensor

great... thanks!!
I figured the same, it runs good and passed the last emissions test.
It looks like it may even be the original sensor, yikes.