[V8] O2 sensor

[Buchholz, Steven]

... IMO you've got to be a bit more careful than this with grounds ... 

The ground wire provides the reference for the OXS signal ... you have
to be careful not to bias the signal because it will cause the ECU to
get an improper evaluation of the state of the car.  There are actually
two ground points on the back of the engine block below the left
distributor.  I heartily recommend that if you are doing the 4-wire
conversion that you connect as close as possible to one of these to
ensure the signal the ECU signal sees is the one the OXS is generating.


To be a bit more detailed about my concerns with the attachment to the
body of the car ... there can easily be a voltage drop between the
engine block and the frame of the car in the hundreds of millivolts.
Furthermore this voltage drop will vary depending upon what loads are
being placed on the electrical system ... coolant fan, head lights ...
even a discharged battery ... and if you attach the ground of the OXS to
the body of the car you will automatically apply this voltage offset to
the signals the ECU is reading for the OXS input.  In addition to this
offset, the long ground path can allow higher frequency noise to get
coupled into the OXS signal.  You may end up with a car that runs well
in the day time but misbehaves at night.  Believe me, ground induced
issues can be a PITA to isolate and resolve ... 

Steve B
San Jose, CA (USA)
> 
> The gray wire is the extra, it needs to go to the other 
> ground. I ran mine 
> to the ground for the aux fan on the drivers shock tower. If you are 
> planning on keeping this car, I'd also recommend getting the 
> plug from a 
> Ford. Any of the 4.6 cars use four of them, so it shouldn't 
> be hard to find 
> one. The colors aren't the same on the plug, but just line them up by 
> position, and connect like wires. The two whites are the 
> same, so they can 
> go to either corresponding white. same for the black wire.