I have a 96 accord ex with an obd1 h swap. i have a cel for heated o2 sensor and my car is running very rich. the o2 bung on my test pipe is on the bottom for some reason so i usually dont plug in my o2 sensor in to it. this weekend i did to see if the car would run a little more lean only it didnt, the light just came on. im not sure if its because i dont have no joke cat or because my sensor is jacked up. thanks for reading

 

OBD1 ?? The secondary O2 sensor [monitor] should not even be considered by the ECM.

Here is some info on the primary O2 sensor;

 

would a faulty o2 sensor cause the engine to run very rich?

 

It will have an adverse effect on gas milage, but as to how rich it might shift things is open to discussion.
At some point the ecm will go to default settings and set the light.

P

 

Im not sure if the 96 OBD1 has a post-cat O2 but if it doesnt and the CEL is on for O2 you likely will have to just replace the O2 and yes a failed pre-cat O2 will affect mileage as it is used for fuel trimming which keeps adjusts your air/fuel ratio to best fuel use.

If it is a post-cat O2 it has zero effect on mileage as it just monitors if the cat is working.