It would be easier to worry more that your engine grounding strap is in
good shape with good clean connections. It's just super easy to go
4-wire from 3 (and cheaper than going stock).

It's not like the sensor is a precision instrument. The O2 sensor is
only good at approximating a lean or rich condition (in relation to the
14.72 parts air to 1 part fuel) based on the amount of oxygen in the
exhaust. It's not good for indicating how rich or how lean. The curve
is not very linear at all. According to some Bosch literature I have,
0.2 to 0.8 volts (approx.) would indicate a "ideal" mixture. Up to 0.2
volts is too lean and over 0.8 volts is too rich. These aren't exact
figures, but you get the idea. The mixture will constantly fluctuate
between rich and lean several times a second to keep the mixture in a
reasonably narrow range. You can imagine the ECU going rich, lean,
rich, lean, rich, lean...must be exhausting. Bad pun not intended,
really. So, if your sensor output fluctuates and your exhaust CO is
good with the sensor disconnected, you're good.

HTH.

Eric Fournier
91 GL

On Sunday, April 27, 2003, at 07:53  PM, Damon Campbell wrote:

> For kicks and giggles, what would be involved in
> tossing in a 4-wire (or 3-wire, obviously) sensor into
> a van with digijet FI?  Is it just as simple as
> triggering a relay off the ecu power source and the
> running the juice from the always hot lead in the
> little black wiring harness box?
>
> I don't know if i'd actually do that, but improving
> grounding in an early model wbx wouldn't be a bad
> thing, either...
>
> Thanks,
> -Damon