I have an 88 F 150 5.0 L and I am installing an exhaust on it without a cat among other things. I called a muffler shop the other day looking for the crossover w/o the cat. The guy told me that if I put this on that I had to put the O2 sensor behind the Y in the pipe in order for it to read correctly. Well I think the original was on the passenger side before the Y. I did change the manifold and the one I replaced it with has a spot right in the manifold for an O2 sensor. Who is right? Does it really matter where it goes? The original wires are only short and therefore could not reach as far as the Y cat or no cat.

 

O2 sensor is the short hand name for Heated Exhaust Gas Oxygen (HEGO). It usually resides in the exhaust pipe before the cat but as close to the where the exhaust from a v8 comes together. The Manifold hole you are talking about is for the EGR, exhaust gas recirculation, that is on the passenger side front of the manifold for the FI trucks. The O2 sensor is needed by the computer to insure the fuel is burning at the most efficient ratio. You can forgo it but you will always pop a code for the engine not having a response from the O2, which COULD cause your engine to lack power.

 

I think what the problem is is that by removing the cat, the only place one o2 sensor can pick both cylinders output if after the y downstream. I know my 1986 F250 5.0 has 2 o2 sensors, one is each pipe.

 

Well the original manifold did not have a hole in it. This is one from another truck, but the original placement for the o2 was in the Y pipe before they came together. I don't think this truck had two 02's. There is a plug on the passenger side that I do not recognize or know what it is for. It is the opposite of the 02 plug, in other words it will plug into the o2 lead. It looks clean so it must have been connected to something. Any ideas on that one?

 

If the hole in the manifold is the right size for the O2 sensor you can use it, the motor will run fine with the O2 sensor measuring 1 side of the engine, my truck has been running that way for years and it passes smog tests.

 

I was hoping someone would tell me that, Have any idea what the other plug may be for?

 

Sounds like that's where the O2 sensor should be connected...

 

One is male and one is female. They will plug together but one I know is o2, the other not so sure.

 

I usually don't put alot of stock in what exhaust guys say, there's a reason they only do exhaust. I don't beleive your O2 is heated, if it's only 1 wire it is not. But they need to be hot enough to run and stay clean, putting it to far from the motor will leave it to cold. I also beleive your truck only had one O2, in the left pipe just below the manifold.