4 wire versus 3 wire O2 sensor.
 

Correct me if I'm wrong.....the difference in the 3 and 4 wire O2 sensors is that the 3 wire grounds thru the case of the sensor....while the 4 wire has an extra ground wire?
It's a Mazda/Chrysler thing from what I see on the net...

http://forums.pelicanparts.com/uploa...1298079533.jpg

So as long as the grounds and power are correct and the sensor fits the bung, a four wire can be used? Reason I ask, I was able to pick up a number of NIB Bosch 4 wires for real cheap....

yes, you don't have to use the heater elements. are these wide band O2 sensors?

I WANT to use the heating elements. It's a good thing......

The heater portion of a 4 wire 02 sensor is monitored by OBDII vehicles. If youre putting this on anything older than a 96 model, its irrelevant.

Why not just get a Ford Taurus O2 Sensor, proper 3 wire.

I would but I have two 4 wires that I got for cheap. Just looking to see if there is any downside on using them....I don't have an OBD engine as it's a 93. But it IS wired for a heated 02.

Won't the O2S ground itself when bolted in?

The 4-wire is a still narrow band O2 with the 4th wire being a signal ground. The signal is only a 0-1V range and simple temperature changes alone can alter the output using the exhaust as the signal ground.

Going to a 4-wire, and actually running the signal ground right to the DME ground point is ideal but simply running a good ground wire to a known chassis ground or to the neg post on the battery are still far better than using the 3-wire grounded through the exhaust.

A narrow band 4-wire can be very accurate and significantly faster responding than a 3-wire. If I was having a hard time passing an emissions test this is one thing I would do.