CIS frequency valve question
 

What is the difference when

O2 sensor wire is grounded
or
O2 sensor is just unplugged

Which runs a higher duty cycle?
Which condition would run richer?

Car in question is a 83' SC

This is just an armchair analysis--I've never done it--but since the O2 sensor generates a signal, I can't see how it would make any difference. Either way, the system gets no signal and runs open-loop with a fixed duty cycle (right?).

Fixed duty cycle but it's not the same in each situation. I don't have an oscilloscope but there is definitely an audible difference
I read somewhere here it's something like 80% if grounded?

John Walker, Loren or Warren probably know the answer to this

ttt

If you want it to run rich, ground the wire going to the temp sensor on the right chain cover. Then, the lambda box will always think the engine is cold and go to a fixed rich setting.