Hey guys, i recently picked up at 99 2.8L A4 as my AWD winter beast. It's got a few issues but what car with 180k doesn't. Recently I received a p0432 code, which most have said usually means the cat(s) are clogged. I suppose I had a few questions that have gone through this before. I've heard 02 sensors can cause this code as well, but since the car has started stalling randomly at stop lights, I figure that one of the cats is clogged. Short of removing the cats and looking through them, is there any way to tell which one is clogged?

I have no problem using a 'universal' cat or even a high flow (test pipe) for better efficiency, as my state doesn't have emissions here. I've heard rumors of some of these still throwing the check engine light though, does anyone have any experience in this regard?

I was also thinking of taking each off (to find out which one is clogged) and shine a light through it to determine their efficiency. Then I could take a long crowbar or something and basically break up the cat (gut the cat) so it's no longer clogged.

Basically, I'm new to the audi world, so not sure what the best stance would be. The car will be my dd in the winter, and isn't a brand new car, so don't need to take it to the dealership for every little fix. Any help is appreciated, thanks!

 

It is possible for the post cat O2 sensor to cause that code. Do you have any other codes at all, does the car just die or does it seem to lack power as well?

 

the car has only died a few times, but enough to make me feel like an idiot in the middle of an interesection. I have only owned the car for a bit, but it doesn't seem down on power. Any way to test if it's the 02 sensor or the cat?

 

Swap the secondary O2 sensors, clear the code, and see if it comes back. If the same code returns, then it's the sensor (since you'd have swapped it to the other cat). If a corresponding cat-related code comes back indicating the other sensor, then your cat is bad.

 

i have the same problem, the description for the code is :main catalyst efficiency below threshold bank 2. i paid $150 to have the driver side cat replaced and still have the same issue, my problem is the car keeps heating up, ive heard it could be because the clog any opinion on that? i just posted a thread

 

im not sure if it's b/c of the 30 degree temperature im in right now, but my car barely gets up to temperature...think it could be related?

 

bumpin this to the top, anyone wanna chime in and share their experience?

 

Cars do not use O2 sensors in open loop mode, when they are first started cold. You can use this to your advantage in checking if a catalytic converter is clogged by simply removing the primary O2 sensor on that side. If the catalytic converter is clogged then removing the O2 sensor will make the car run much better in open loop mode. Of course, it can't really be driven that way because it won't work for closed loop mode when O2 sensor input is actually very important. Make sure there're no flammable objects around the O2 sensor hole if you do start the car with it missing.