The cat and pre-cats on my 380sl are undoubtedly plugged up because the car has been burning oil, and the law requires the car to have a cat but not the pre-cats. So, I was thinking about reaming the pre-cats out to let the system breathe better, until I can get enough money together to replace the whole system with a stainless steel one.

Before I do, however, I was wondering if reaming the pre-cats out would negatively affect the way the car runs by, say, increasing the CO the O2 sensor sees, thereby, causing the sensor to alter its output to the Idle Control Unit?

In addition, I was wondering from a strictly hypothetical perspective whether reaming out the cat on a car with a cat that's downstream from its O2 sensor would affect the sensor's output the same way reaming out upstream pre-cats would?

Thanks in advance for any insight anyone can give me on this.

I got rid of mine,and newer car,did not affect anything

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

Are you saying that you have a non OBD2 car with a O2 sensor after the pre cat?

The O2 sensor needs to read what the engine is making not what the treated exhaust looks like.

On OBD2 ( post 95 ) cars, there is a post cat O2 sensor but, that is used to monitor cat quality.

I have a newer car with a precat oxygen sensor,and after cat sensor,I welded steel tubing in place of cat no problem,and every other car I owned with cats.from late 70s to 99.They make test pipe for most cars to test power without the cats.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

One car I gutted cat with a brass drift tool.Its like a instant 25 hp.my brass drift is four feet long. I break the material,then start car to expel the mess.Then hook back up the exhaust

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1999 w140, quit voting to old, and to old to fight, a god damned veteran