O2 Sensor wiring questions
 

Greetings folks.
Further down the road on the 'Huge Flat Spot' Thread.
Data to date:
Huge midrange bog.
Air Flow Sensor pulled, cleaned w/ alcohol, wiper tension slightly increased.
Air Flow Sensor adjusted to a minimum of 0.9 volts.. would not dial down to 0.6-0.7 range.
Duty Cycle Cold = 50% exactly
Duty Cycle Hot = 8-10%. Once warm, Pin 3 voltage ramps up from 6.6 VDC to 12.3 like it was on rails.
Duty Cycle is non-responsive to unplugging/plugging O2 sensor.
Duty Cycle is unresponsive to mixture adjustment via adjuster 'screw' (allen).
O2 Sensor putting out 0.95 VDC, measured at sensor plug.
Exhaust system has continuity to engine block & to B- on battery.
O2 signal is (apparently) not making it to the control unit (will be checking tonight or tomorrow).
Car is now drivable, now that I've unplugged the EHA connector.
The bog was due to running waaay rich in the midrange. There is still some (barely perceptable) over-rich condition at midrange, i.e. on acceleration from midrange, engine picks up speed slowly, then faster if I back off the gas.

Question 1: Will the engine fire and run with the controller unplugged, so I can verify that the .95 VDC signal is making it to the plug, or should I keep the engine off and just check for continuity, and that the signal is not being shorted to ground, or to the shield.
Question 2: Has anyone encountered broken wires / solder joints, or other 'loss of O2 Signal' situations.
Any BTDTs would be appreciated.
Thanks in advance,
Mark

Sounds like a 1986-93 model with CIS-E, what year & model are you talking about?

You got it. Its a '90 300E.
Thanks for responding. I was hoping you'd jump in on this at some point. The original thread was 'Huge Flat Spot", started over a week ago.
I'd like to be making better progress on this, but work keeps getting in the way...
I have also run across a Service Bulliten mentioning issues at the Control Unit plug, solder joints, shorts to shields, all manner of horrors.
Do you agree that the diagnostic trail points in this direction?
Did the '90 year have issues with engine harness's?
Mark