Cat question
My guess:
- The cat probably just doesn't perform well enough.
- The manufacturer didn't want to pay for CA certification.
Typical causes of this:
- A broken substrate in the Cat.
- Contamination of the Cat. (By using the wrong type of RTV on the engine, etc.)
- A bad O2 sensor.
So, you might want to have someone who can do O2 sensor scans to check your stuff out. (A special scanner that shows the sensor waveforms is needed.) I'd hate to pay for a new Cat and then find it didn't fix the problem...
If you tap on the Cat and it sounds like broken glass, loose marbles, or a maraca, its probably an indication that the substrate is bad and needs to be replaced.
They are typically made from a ceramic substrate coated in platinum. The better ones have... more platinum - that makes them expensive. BTW - Don't throw your old one away, its worth money!
If you do change it, I wouldn't advertise the fact. Theft of Cats is common and I'm sure people who do that would love to get their hands on a brand new one! (That may be another reason to look for a good used one.)
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Often times the cat material isn't acutually clogged nor broken, it's just inefficient at filtration due to loss of this "coating", and the O2 sensor indicates this through loss of oxygen storage capacity of the cat. The rear O2 sensors respond too quickly (in relation to the fronts) to changes in the A/F ratio commanded by the PCM. This code does not specifically indicate any melted/clogged/broken material (just loss of oxygen storage capacity - hence, "inefficient" as the code states); you will notice driveability and performance issues if exhaust flow is actually blocked by melted/clogged material.
Usually, a cat only becomes "clogged" due to misfires or other conditions that cause large amounts of fuel to be dumped into them, thus overheating and melting the material, and/or weakening it and breaking it apart. Impact damage can also cause them to break apart.
It sucks if you live in a state where you actually have to worry about this. I started seeing that code right after the extended warranty ran out on mine, so I opted to do absolutely nothing about it. O2 sims/custom tuning is all that's needed to pass my local emissions test, so the decision was simple for me....just leave it alone. The cat never became clogged nor broken, driveability/power/MPG never changed a single bit - the cat just doesn't filter properly any more. This happened last summer, I had mostly forgotten about it until reading this thread.
Last edited by RPM WS6; May 13, 2012 at 02:33 PM.
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