I am working on my son's '84 which is running too rich to pass California emissions. With a brand new O2 sensor, I get the following symptoms. Hot,idle gives 0.85 volts at the disconnected lead so it is in fact running rich. I get little response to leaning the engine by creating a vacuum leak. Voltage on the O2 input to the ECU is 0.5v with the O2 sensor disconnected (I suspect that is the default). However, when the O2 sensor is reconnected, the voltage stays at 0.5v. There is no drift down to 0>5, it flashes to taht as soon as the connection is made. Wiring checks out per the Bentley table. Does this indicate a bad ECU or is something else determining the voltage?They are too expensive to "Easter egg"
  Any thoughts would be appreciated?
TIA,
Steve
'81 Country Home Myrtle the Turtle
'84 Vanagon (temporary custody)