Can anyone tell me the factory location of the O2 sensor on '89 F250 5.0L. Is there one or two on this engine. P.O. cut off the cats before the Y and welded in duals? There is a very short cross-over between the pipes with what looks like an O2 sensor installed but there is also what looks like an O2 sensor in the passenger side manifold, which has no wires attached. If the one in the manifold is factory, why disconnect it and put one in the H-pipe?

 

I don't believe the 89's had one factory mounted into the manifold...but, the little crossover thing is the correct factory placement for the O2 sensor. it's possible that sometime in the past the manifold developed cracks and he replaced it with one from a later model vehicle.

 

Thanks for the reply. It is quite possible that it is a replacement manifold because the other side is cracked and needs replacement too.