Cat converter question, 4.4i/4.8is
 

My Bank 2 Cat is failing, but the OEM converters are now NLA. Do the cats from the 4.4i (N62) work on a 4.8is?

TIA.

If they are "barely breathing" you can likely punt on replacement with some c
O2 adapters. Are you getting low efficiency error tripping SES?

I added a couple $9 brass adapters and solved the errors on wife's 3.0 about 25 months ago no errors since.

I'm not having any drivability issues, but the code is:
"Catalyst System Efficiency below threshold"

I don't think the spacers will fly here as they inspect under the car with mirrors when you go for inspection, even though they do a plug-in to the OBD.

They are definitely not the same part numbers on RealOEM, but that doesn't necessarily mean they won't work.. though I would suspect there may be just enough difference to screw you up. I wasn't able to actually determine the cell count for each unit, but I would guess with higher displacement of the 4.8 that they are different.

That said, since they have to come down anyway maybe you save yourself a few bucks and some back pressure and find a good shop who can weld stainless and toss on a pair of high flow (legal) cats? Just thinking out loud.

Always a thought. I have found a used one. But I’m not sure how many miles are on it I asked the seller so we’ll see what he says. It looks like this happens once in a while but it’s not a really big problem for these cars so I’m hoping the used one will be fine.

Agreed [emoji106]

Would be the simplest/easiest way to go for sure.


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The angle adapters I use still require a working cat. It doesn't eliminate the cat

Yeah, I'm pretty sure mine "works" but I won't know until I get it out of the car. In the mean time I located a 67K mile cat that is claimed to work 100%. It's on it's way to me. Will update with progress.

You can tell if it's working by monitoring the post cat O2 sensor voltage.

If it doesn't track the pre cat voltage it's still working. If it basically looks the same as pre cat is shot.

It can be the sensor. I would maybe swap left and right post cat sensor. If the error swaps sides it's the sensor.

I definitely would try to confirm exactly what's going on before cutting any exhaust tubes.

I did check the sensor outputs with INPA, nothing looked unusual.

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