I have a 90 with header with a one wire O2 sensor and since I have a header, the O2 sensor is located in the downpipe, near the cat. I heard that the 92-93 had a 4 wires O2 sensor because the sensor is far from the engine and thus needed the heater to assure they are at the good temp to send optimal readings. Could I convert my one wire to a 4 wire sensor? why 4 wires? I know one is for the signal, 2 for the heater, but what does the 4th one? Knowing what are doing the 4 wires, I could probably rig something up to control the heater… maybe this would help my bad gas mileage and bad idle.
nice… Now, is the heater always ‘heating’? Meaning I could screw a 4 wires O2 sensor into my donwpipe and connect the heater to a ‘hot when running’ accessory and i’ll be good to go?
Just found the answer! I found a website where a guy retrofitted a 4 wire O2 sensor into his miata… he simply connected the heater wires to a ‘hot when running’ accessory!