I need to replace the O2 sensor on my 89 spfi and I'm wondering what three-wire sensor will work?

Can I just use one for a Legacy?

 

Yes, I know it's a one-wire in there, I want to convert.

All O2 sensors have the same thread size/pitch. Any three wire will work if you have the schematics. As covered in another thread, you're not going to see any kind of performance gain from doing this. Mileage or otherwise. The heater was introduced strictly to bring the sensor to proper operating temp faster to reduce start up emissions. It doesn't affect anything else.

Well, obviously I'll see performance and mileage gain with a new sensor because mine is pretty much dead.

But, my reasoning on the three-wire was this.

The cat probably doesn't work anymore, if it's not already gutted.

The cat usually runs at a pretty high temperature so it keeps the O2 pretty warm, but with the cat not working, the sensor won't be as hot. I thought that could cause some performance reduction in the sensor.

 

If I'm wrong, I'll just get a one-wire because they're cheaper...

In case you didnt see it

 

http://www.ultimatesubaru.org/forum/showthread.php?t=128967&highlight=3-wire+o2+sensor

 

 

I thought that could cause some performance reduction in the sensor.

The only issue you may have is at idle, I want to try this mod but I cant seem to find my extra 3-wire I had. Might just be in my head, but I notice a difference in idle quality between open/closed loop.