O2 Sensor questions

[lehass]

I have a 1990 2.9L Ranger that has 268K miles on it and I know that the o2 sensors have never been replaced. I can only find one right before the cat. Is there any others on this engine or is that the only one. And since the vehicle is "broken in" could the o2 sensor go bad or malfunction without ever throwing a check engine light?

 

[sjr53]

There is just the one O2 sensor and that is way more mileage on it than it was meant to handle. You may get a gas mileage improvement that would cover the cost of a new sensor and O2 wrench/socket needed to easily replace it.

 

[enjr44]

Something like two and a half times.