O2 Sensor Bypass/Delete

[MDOverlander]

O2 Sensor bypass question…
So, to put rock sliders on my 96 LX450 (35s/529 gears) I had to cut out the cats and replace it w a straight pipe. The rear part of the pipe w the downstream O2 sensor was also cut out. So, there is no rear sensor just an empty plug. Obviously the check engine light is on. I’m worried that it may be running to rich because that’s the default setting when the O2 sensors aren’t working. So, I’m worried about fuel consumption and carbon buildup. Otherwise, it currently runs well. Has good response and doesn’t smoke.
Options to fix the issue if I don’t want to replace the cats and get new pipes?

What will happen if I simply get a down stream sensor and leave it open to air? Will it run too lean?

Should I clear the code and see if there are any changes in performance? And, if not leave it alone since it’s not running too rich?

Let it run rich and use some Sea Foam or MMO to clean out the carbon buildup?

From my in line search…
I can buy a new down stream sensor and increase the resistance of going from the sensor to the computer (picture). However, I don’t have a place on the exhaust pipe to plug in the sensor since it was cut out. So, the sensor will be open to air.

I can also purchase a simulator. But, I still don’t have a way to plug the sensor into the pipes

Any thoughts?

 

[devo]

Interesting

 

[YMT]

Short answer, the O2 sensors need to be in the exhaust to avoid running rich.
You can buy a bung to weld into your new pipes.

 

[OffRoadScott]

You will need something like this. I ran it on my 03 WRX after I put on a cat-less down pipe and it never threw a check engine light.

It is called a spark plug anti fouler.

 

[originalhobie]

You will need something like this. I ran it on my 03 WRX after I put on a cat-less down pipe and it never threw a check engine light.

View attachment 3447781

It is called a spark plug anti fouler.

Hi Scott,
I’m also having an issue like this. I recently purchased a 92 and the cat has been removed with straight piped installed. Since I’ve had it, it smells like it’s running rich. I’ve crawled under and cannot locate a second O2 sensor.
Where would I place this spark plug anti fouler?

 

[originalhobie]

Hi Scott,
I’m also having an issue like this. I recently purchased a 92 and the cat has been removed with straight piped installed. Since I’ve had it, it smells like it’s running rich. I’ve crawled under and cannot locate a second O2 sensor.
Where would I place this spark plug anti fouler?

 

[originalhobie]

Hi Scott,
I’m also having an issue like this. I recently purchased a 92 and the cat has been removed with straight piped installed. Since I’ve had it, it smells like it’s running rich. I’ve crawled under and cannot locate a second O2 sensor.
Where would I place this spark plug anti fouler?

Dumb question. Never mind.

 

[subiefiles]

Downstream O2 sensors (post cats) would be only for emissions purposes and not have anything to do with how the engine runs. So if you can trick those with spacers / “anti-foulers” so the CEL goes off, you’ll be fine.

The upper/front O2 sensor(s) are what dictate how the motor runs. You want those to be working as designed

 

[MDOverlander]

Downstream O2 sensors (post cats) would be only for emissions purposes and not have anything to do with how the engine runs. So if you can trick those with spacers / “anti-foulers” so the CEL goes off, you’ll be fine.

The upper/front O2 sensor(s) are what dictate how the motor runs. You want those to be working as designed

Doesn’t the upstream sensor compare the O2 w the downstream sensor to adjust fuel ?

 

[subiefiles]

The downstream sensor is only there to measure catalyst performance, since there is nothing else between the upstream and downstream sensors besides the cats