I changed the o2 sensor on my son's '91 F150 302 AOD, hoping for a little gain in MPG. It looked exactly like the one I removed. A bosch unit, got it from Rockauto.
He indicated this morning that it was backfiring while accelerating from a stop and when it shifted gears.
Couple things; could an o2 sensor R&R cause a backfire? Is there a torque spec for an o2 sensor? Could I have overtightened it?
First thing I'm going to try is replace it with another sensor, since it ran pretty good prior to replacing it.
Anything else I might check while I'm poking around?

Thx.

 

Look for any exhaust leaks. Maybe around the sensor bushing or where the pipe joins to the manifold, maybe the joint was disturbed when fitting the new sensor.