Hi guys,

I recently bought a used 8 and i was trying to get familiar with what's changed on it.

The OEM catalytic converted is not there, a pipe is welded in its place (not sure if there is cat in it) and the O2 sensor is also plugged in there with some cabling coming in the cabin for AFR gauge to work.

No CELs or whatsoever appear, but the gauge was broken ( cracked ) so i decided to remove it.

Unfortunately while trying to get the cables off, i accidentally cut the O2 sensor cable.
So now the O2 is screwed in the Cat pipe, but no cables connected to the car

So i fucked up i guess.

Would this cause any issues to the car ?
Should i replace the O2 with another O2 and connect it back ?

I get some rough idle but i got new COILs at the same time, which i believe are fake, and i believe this is caused by coils.

I am going to get old COILs back, but i want to know if rear O2 is required to be connected back to the car.

P.S: I run the car like that now, and i dont get CEL for o2 or cat.

Thanks,

 

The main narrowband O2 sensor that the pcm uses is located at the upper end of the exhaust manifold. That sounds like a secondary wideband O2 sensor that was being used to monitor AFR. If you removed the gauge then it doesn’t matter.

 

i removed the gauge but the cable connected between the o2 sensor (catalyst) and the car is disconnected. is this again ok?

 

Maybe you should take some basic automotive classes or befriend someone with experience to help and teach you.

 

then lets close the site and all go to classes thanks for ur reply. i am trying to exclude possible causes of the rough idle. anyway.

 

Well if I was rude then I apologize. Maybe it’s the language difference, but my original response clearly explains the situation to an experienced person with comprehensive English language skill. So your question seems to indicate you don’t understand much about the RX8 and/or my English explanation.




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im not an rx8 specialist nor a car engineer.
my question was simple, i cut the rear ( downstream ) oxygen sensor cable, it's still installed. Will this have any impact on the car's drivability or CEL ?

I completely understood your answer, "it doesnt matter". My question was a bit more specific.

 

Well that depends. There are two factory O2 sensors. That sounded like an additional, i.e. secondary, sensor that someone installed in the exhaust system to monitor AFR via the gauge. You typically wouldn’t tap into the factory sensor for this, but then you can never be sure of some people. So you need to verify that the two factory sensors are in place and connected properly.

The front factory O2 sensor is what the engine uses for fuel control. It’s located on top of the exhaust manifold a few inches before where the exhaust manifold and cat/mid pipe flanges bolt together. The wiring for it should run up to the top of the transmission bellhousing where it bolts to the engine.

The rear factory O2 sensor is located in or behind the cat converter. All it does is monitor cat converter efficiency. It will cause a CEL code indicating if the cat converter is working properly or not, but not affect engine performance. The wiring for it should go over to the transmission and attach to a connector on a bracket on the side of the transmission where the tailshaft housing bolts to the main trans casing. This would be for a manual 6-spd trans. I’m not sure for the 5-spd or auto trans.

If it just an extra sensor you can either remove it and install a plug or you can cut the wiring off and let it be the plug. Your choice.

So as long as the front factory O2 sensor is still in place and wired correctly then whatever else you have should not be affecting how the engine runs. If there isn’t a cat converter then the rear factory O2 sensor doesn’t matter because either way there will be CEL light and code thrown regardless of whether there’s a sensor or not.

I hope this helps. Sorry if I wasn’t patient enough before, but it’s a bit painful to have to type out detailed explanations for people who don’t understand the basics. Teaching people in person is much easier and enjoyable, but time consuming and not fun over the web.


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I understand your frustration, but unfortunately this is the nature of this forum.

i appreciate you found the inner strength of yours and writing in detail what i needed to know.