O2 Sensors

[SCOTT]

I have a 5.0 out of a 97' mountaineer. Which has the EEC IV computer. The wiring diagram shows 4 oxygen sensors, two before the cats and two after. I am currently not running any. But I am a little concerned wether I should or not, and if I should, do I need all four sensors?<br>Any thoughts?<br><br>Scott

 

[77bronko]

One of the benefits of FI other then the ability to offroad better, is fuel economy. This does require the O2 sensor so the engine will run right during steady state conditions such as idle, and cruising. On the ORIGINAL engine the FI came on, even without the O2 sensor if everything else is functioning properly, you should get better economy with FI then with a carb.<br><br>If the engine is different then the original with headers and less exhaust back pressure, and a better less restrictive intake or any other modifications, I would be worryed about the engine running lean if there is no O2 sensor feed back. This problem is even more exagerated if it is a MAP based as opposed to MAF based FI system<br><br> I believe, but not 100% sure, that with that system you can get away with only the two before the cats. But you will need at least 2 for that compensation function to work right. <br><br>If you had catalyst in your exhaust you would need to run with a functioning O2 sensor otherwise you would ruin the catalyst.<br><br>

 

[alex69eb]

The rear o2s ar4e not needed they are called catilyst monitors. They are only used to verify the cat convertor is functioning properly, You only need to use the front 2 for the computor to run the vehicle in closed loop. not having the rear o2s will set some dtc's or codes. no big deal though. engine will operate in closed loop without them. You can also emmit the o2s completely try it on your own car and see if you can tell much of a difference just crawl underneath it and unplug the front ones will run a little rich but not at all bad. really you can run the vehicle without the maf, or the o2s and several other sensors and the vehicle will run on preset computor values but the default is always on the rich side. But with only the o2s unplugged the vehicle will run fine.

 

[Broncobowsher]

The computer you have (if it is the stock one for the mountaineer) is an EEC-V, not the EEC-IV<br><br>You will need the 2 pre-cat O2 sensors. They are the ones that provide feedback to keep the engine running right.<br><br>The post-cat O2 sensors are part of the OBD-II system. They monitor the exhaust after the cats to make sure the cats are working. If a cat goes bad, the secondary sensor will cause the check engine light to come on.<br><br>Unless you transplant every sensor and probably even the fuel cap, the check engine light will probably be on. The OBD-II does not like to b fooled. There are even sensors for the fuel temperture and tank level in some cars.<br><br>I have heard that some places can reprogram the ECM to ignore the OBD-II nuscence codes. If I knew the name I would tell it to you, but I don't know it. Check with the mustang tuners. They could take out stuff like evapo pressure and post cat O2 sensors but keep stuff like cylinder misfire (it is so nice when the ECM tells you #3 is misfiring).

 

[SCOTT]

Thanks alot guys. I think I will run the two sensors before the cat to be on the safe side. I called ford to get the sensors and they want the vin# off the Mountaineer, unfortunately I don't have it. So, I hope I can get by with a universal oxygen sensor.<br><br>Scott

 

[edge4]

Scott,<br>I read in the Probst EFI manual that the O2 sensors are the eyes and ears of your EEC-IV. They are the most important sensor in the system. I would recommend at least two as close to the collector as possible, where the heat and backpressure is sufficient. Pull the part number off your EEC-IV to find the matching O2 part number.