rbc123

Am I doing any damage by driving with a bad cat converter?
When I say bad I mean has the rattle and throws code after being cleared and driven 50 miles or so.
I thought I had a deal with a rennlister for a set of used cats but he no longer answers e-mails or PMs.
So I am back looking for a set of used cats for 03 cab tip.

RBC

DBJoe996

Somewhat depends on the code, but here is my understanding: the DME (engine management computer) is constantly taking readings from the O2 sensors before and after the cats and adjusting the air/fuel mixture for each individual bank of the engine, as well as spark and camshaft adjustments. It is all very dynamic and also varies with engine speed, load and vehicle speed. It just seems logical that a bad cat will trip certain values programmed into the DME and it will adjust accordingly, meaning either leaning out the mixture on that bank or making other adjustments to compensate. To me, not a good scenario. Not saying don't drive it because it is going to explode. Just get it fixed asap.

kromdom

Magnaflow sells bolt-on/exact fit cats for under $500 each (after discount). To get the 5yr/50K mile warranty, install must be done by a shop. Will pass visual and sniff test when smog time comes. Best of luck.

P.S. make sure you buy from an authorized dealer for warranty reasons as well.

rbc123

the code is P0420

DBJoe996

So prevalent it has its own website http://www.p0420.com/

Given the rattle and code (says Bank 1 so drivers side/left side of engine), might as well plan on replacing both cats and moving on.

kromdom

+996...which is exactly what I did (FWIW, it was also my driver's side that failed but no rattles at all, just a persistent 0420 code)

OKB

a cat can cause restriction in air flow and even prevent air from exhausting completely, it can decrease power till it wont accelerate

Cuda911

Excellent link, Joe! I've been battling the dreaded P0420 ever since I replaced my rattling OEM cats with a Fabspeed system.

Mike_A

Will the installation of a cat bypass system always (most probably) pop a 0420 code on a street 996?

Ahsai

Yes and you can count on it

I agree with Joe's comments above.

Copilot

So other than unnecessarily killing the environment, what damage does/can running a catless exhaust do?

laphan

Well, as I mentioned in my reply pm to you, you can have mine. It has 85K miles and no rattle or check engine light. I removed it due to some exhaust rattle. Thought it was the cats and replaced them with low mileage used cats. Rattle turned out to be exhaust shield was touching the muffler. I basically replaced a set of good catalyst.

Make an offer, I have no set price, just trying to help...
You pay actual shipping.

If RBC doesn't want the cats, offer stands for any rennlisters who needs them. If not, I am going to keep them as spare.

m3driver

If you run spacers on your post cat O2 sensors you will not pop a code

laphan

Another option to run catless: http://www.magnumtuning.com/en/detail/ez-cel-fix-oxygen-sensor-simulator/porsche/carrera-996

Mike_A

So, that takes the business end of the probe out of the exhaust stream and essentially fools the DME?