3FE O2 Sensors - 1 or 2? (1 Viewer)

[PabloCruise]

Search fcn rejects me saying O2 is too short or common...

I have a 3FE in a Pig that has been hooked up with 1 O2 sensor.

So far I have stumbled onto threads debating whether 1 or 2 O2 sensors are optimal.

Can anyone help me out as I am not sure how to get Search fcn to produce for me...

 

[Mark W]

Your EFI treats the engine like it is a pair of 3 cylinder engines...
that is why there are two sensors


stick with two.


Mark...

 

[Mace]

Your EFI treats the engine like it is a pair of 3 cylinder engines...
that is why there are two sensors


stick with two.


Mark...

So if you pull the O2 sensor out of one side the engine will start dumping fuel into that bank of three only??

 

[alkaline747trio]

Yes, unless there is a failsafe mode where it auto reads one for the whole system.

 

[PabloCruise]

Your EFI treats the engine like it is a pair of 3 cylinder engines...
that is why there are two sensors


stick with two.


Mark...

Can you tell me what is going on right now that the two harnesses are looking at one sensor?

 

[Mace]

the sensors are just looking at a averaged signal between the two sets of banks. Not a huge deal from what I have seen but I have never done it myself.

 

[PabloCruise]

If I have a custom exhaust after the manifold (think 3FE into a 55), where should I place the 2 bungs?

 

[Mace]

one in each bank at the merge point (or so)

A pic of your exhaust would help

 

[PabloCruise]

one in each bank at the merge point (or so)

A pic of your exhaust would help

Roger that, I will get exhaust pic up

 

[PabloCruise]

one in each bank at the merge point (or so)

A pic of your exhaust would help

O-k, these pics are less than ideal, but it is late, dark, and rainy...

If these are not enough info, I will snap pic when it is better access to the underside:

 

[Mace]

Just put one in each of the Y pipe legs.

 

[PabloCruise]

I am bringing this topic back up...

I still have the one o2 sensor hooked up. I recently determined it was dead, so I replaced with new Bosch o2 sensor, same location.

I am fighting an issue where after the 3FE is heat-soaked, I gradually lose the ability to idle.

The idle will break down to the point where if I don't blip the throttle, it will die. It will get so bad that even putting throttle wide open does not save it. But if I act before things get bad, say take it out on the highway, it will run fine until I let it sit and idle again.

Can anyone share their experience and/or expertise?

Are these two related?

 

[Zezima288]

Sorry to bring an old thread back to light, but have you ever figured out your idle issue? My 3fe is acting the same way you described yours, I've replaced both o2 sensors, spark plugs/wires, and MAF sensor. Maybe distributor rotor and cap?

 

[LAMBCRUSHER]

use search to learn how to pull trouble codes and pull them. post up the codes here. find the link to the FREE factory service manual downloads in classifieds and read all pertinent information. you have a few likely culprits, but you're going to need more info to get us more info to make you get us more info for us to give you info...savvy?

 

[LAMBCRUSHER]

edit...post up the codes IN A NEW THREAD you start for YOUR RIG...to help keep things clean on the forum...

 

[PabloCruise]

Sorry to bring an old thread back to light, but have you ever figured out your idle issue? My 3fe is acting the same way you described yours, I've replaced both o2 sensors, spark plugs/wires, and MAF sensor. Maybe distributor rotor and cap?

I did solve it!
See here for my long, boring story, plus pages from the FSM regarding trouble codes: 3FE - Codes 12 and 41