I've got a buddy who has either a 1993 or 1994 F-150 2WD 5.0L. He wants me to put a set of Summit's FlowTech long-tube headers on it.

But, we have a dilemma.

From the factory, these trucks have the O2 sensor in a small crossover-tube in the y-pipe. This gets a "combined" reading from both banks of the motor. As far as I can tell, this is the only one.

He's got the collectors for the headers which have an O2 sensor bung in each one. So, that equals two O2 sensors. From there, he wants to run true-duals.

I'm guessing that he wants to "splice" the sensors together, but I have my doubts on this working properly.

What I think he needs to do is send back the O2 sensor-compatable collectors, get standard collectors, have the muffler shop fab him up a y-pipe, put the O2 sensor in it, and run his duals from there.

BTW, the O2 sensor needs to be as close to the motor as it can get, right?

Any insight is appreciated.

Nightrain

 

Splicing the HEGO's is a bad idea. Standard collectors and an H pipe should get what is needed done.

Another option is a MAF conversion. You'd need 2 HEGO's for that and the collectors with the bungs would be good to go. Granted that's another $700+.

 

No, the Flowtech's will work just marvy. Plug the hole in the drivers side header and just use the pass side location for the single O2 sensor. Yes... it's that simple. My speed density '89 5.0 work perfectly for years with this exact setup, and my SEFI mass air 5.8 also has been functioning perfectly for years with a single O2 sensor.

P.S. If you find the O2 sensor wiring is a bit short,(some sensors have very short pigtales) take the time to unwrap the wiring from the harness where is comes up from under the motor. I gained nearly a foot extra length doing this.

 

If you follow Cananski's suggestion be aware that this is a small risk. If something happens on non-sampled side to cause a lean condition, you probably would know it until after you've melted a piston or two. It is a small risk, anything that could cause this should effect both sides, but...

A variation would be to get a cheap O2 gauge and hookup the second one to the gauge while the first one is talking to the computer. It's less expensive than the MAF conversion but still covers both banks.

 

The MAF conversion still only uses 1 o2 sensor....the signal is split into both banks on the computer pins.

My vote is to duplicate the stock configuration as much as possible.

 

Thank ya'll very much for the suggestions.

I'll put his headers on with the standard collectors (they're cheaper than the O2-compatable collectors, anyway), then send him to the muffler shop to have a y-pipe fabbed and put his O2 sensor right where the pipes come together.

Thanks again!

Nightrain

 

i'm currently putting headers on my truck and i noticed that there is no O2 sensor, the plug in is just hanging, there. Since their isn't a O2 sensor my emissions light should be on right? and i know that light works, cause it comes on when i turn the key on, any suggestions?

thanks, chris

87 f150 302 a4od

 

So are you saying your truck has no O2 sensor at all? If so it should be running badly.. puking through fuel like there's no tomorrow. And yes, the check engine light should come on as soon as the engine gets up to operating temperature. Do your headers have an O2 sensor bung?

 

Are you sure? I'm the first to admit that I haven't done the conversion and don't have a stock MAF either, But...Every wiring diagram and chart I've come across shows a L HEGO and a R HEGO for EEC-IV MAF/SFI systems.

Nevermind. Those are Mustang diagrams I was looking at. The Truck diagrams only show 1 HEGO at pin 29 while the Mustangs show 1 at 29 and 1 at 43.

 

I have to agree with SR_Crewchief, there are EEC-IV MAF setups that have two 02 sensors and the computer has separate pins for them, L and R. Perhaps MustangGT221 was referring to using a mustang computer setup for the conversion and that computer only has a single pin on the computer for the O2 sensor.

 

The Ford mass air conversion kit splits the single O2 sensor signal to the two input pins on the computer (89-93 mustang computer is what's in the kit), and that's also what I did when I made my own mass air conversion harness (also using an 89-93 mustang computer). Stock EEC-IV mass air trucks only use a single O2 sensor as well. The EEC-V trucks had 3 O2 sensors.

 

That's interesting. So Ford decided that even though they have a computer that can take a left and right O2 sensor reading that they will only use one O2 sensor. I guess since it was placed in the the y pipe collector where the exhaust from both sides of the engine come together that the reading would get averaged out so why not just split the single and save the cost of having two sensors. There probably would be very little to gain from having two as long as everything is running properly.

 

Yeah, it makes the install of their swap kit much, much easier. No drilling, tapping, or welding in bungs, just plug in the overlay harness and computer and it's ready to go.

 

there are no O2 sensors on my truck, i noticed while i was removiing the manifolds, adn yes my truck runs beautifully,

 

Must be carburated then...