CIS Lambda wire grounded vs. not grounded?
 

Can anyone out there explain what happens on K-jetronic when the O2 sensor wire is gounded as compared to just unplugged?

I've been doing some testing and found that when I ground the wire to the lambda computer it runs a little bit richer when compared to the O2 sensor unplugged and the wire not grounded.

I'm trying to understand why and appreciate any help.
Thanks.

Sam,
I have been investigating something similar in attempting to track down my poor fuel mileage. My Oxygen Sensor wire was grounding off to itself (I did not know at the time it was a shielded wire) which produced a very rich mixture, poor fuel mileage (17.70 highway), and a very fume laden exhaust smell. The overall performance of the car was good though. In reviewing Wayne's 101 projects book, he gives an example to disconnect the Oxygen Sensor and ground it off to the frame which does indeed make the ECU think the mixture is lean and richens the mixture up - which is exactly what you described. Before I wised up and separated the Oxygen Sensor wire from the grounding (shielded portion) my output from the Oxygen Sensor was ignored by the Lambda computer and no changes in the mixture were ever made.

I, unfortunately, do not know if there is any difference in mixture between simply unplugged versus grounding the wire. I am in process of installing a circuit where I can go from closed loop to open loop with a flip of a switch which should permit the higher level of performance offered by the slightly more rich mixture as well as providing the much better fuel economy offered by the closed loop - at the discretion of the driver!!!

http://forums.pelicanparts.com/uploads/richstop.jpg

Tom