Oxygen Sensor, For the California Folks Options

[gfg3]

I have a '75 1.8 FI car that originated in California. This car originally had an O2 sensor, but now it doesn't. I'm looking to replace that O2 sensor. I've been told that the O2 sensor hooked into some sort of relay which then ran back to the computer. First, is that correct? Second, does anyone have a photo of the O2 sensor hookup from the exhaust all the way to the computer? If there really is a relay in this scheme I could also use a picture or description of that relay too. Once I figure out what I'm looking for I'll try to find the parts. Thanks.

George

[PancakePorsche]

75/76 California cars:
The relay in the trunk is temp control relay which reads the thermocouple in the thermal reactor. It usually will only trip if spark plug fouls or MPS failure which puts excessive raw fuel into the reactor causing it to overheat therefor damaging it or drastically shortening it's life.

For further protection it also has fuel cutout rev limiter instead of ignition (sister board on battery tray), and decel fuel cutout in the ECU below 2K rpm with full off throttle. Very annoying in slow traffic.

[gfg3]

Thanks everyone for your comments - as usual, very helpful. The catalytic converter is no longer on the car, so it looks like I don't need that relay. But the question remains: how does the O2 sensor hook in? Through that same relay?

And for matthepcat: no, my area of Virginia doesn't do smog checks. The reason I was looking to hook up the O2 sensor again was to see if it would solve a problem with the engine running very rich at idle. Car has all new wiring, and all the usual suspects (aux air regulator, throttle valve switch, MPS, temp sensors, etc.) and vacuum lines have been checked and/or replaced. Fuel pressure both with and without vacuum is spot on. Car runs and idles just fine. I thought that the '75 computer may be looking for an input from the O2 sensor to control the mixture at idle. My thought was to hook an O2 sensor up the tailpipe and connect it to the harness and see if that made a difference. If so, I'd permanently install an O2 sensor. Really grasping at straws here.

Thanks again.

George