My 997 bucking/misfire

[Silver_TT]

If the cats are broken inside you can hear it very easily. Shake the cat and you should not hear anything. If you shake the cat and it's broken, you will hear the broken element pieces inside. Some folks say you can test by hitting them with a rubber mallet with the cats still on the car......however, if you have the cats off the car it will be trivial to tell. Also, when you go to a scrap yard to get $ for the old cats, I noticed they poke into the cat with a long stick........... if they can poke far into it, that means the element is totally broken up. They use this as a very rough estimate to try to figure out how much of the cat is broken up inside.

Edited March 2, 2014 by Silver_TT

[JFP in PA]

Thanks for you reply.

What do you think if i put my original cats back and test the car? Btw i store my original cats in my storage house out from the box, any problem with that? How i know if my original cats are broken inside?

Before I would be unbolting anything, I would be doing some of the suggested diagnostics to see if the sensors are working correctly; if you swap the cats and it was one of the sensors, you will be no better off than you are right now, but a lot more dirty and tired. And if you swap out all the sensors, and it was the cats, you would be in the same position, but out a lot of money unnecessarily.

Silver_TT is spot on about the old cats, they should have no moving parts and make no sound when you shake them.

[binger]

JFP & Silver TT are right on track. One more note to add you should look at the fuel trims to be sure that the DME has fuel control. If one or more of the o2 sensors, injectors, fuel pump, vacuum leaks / pirate air, are giving bad feedback to the DME that could damage or even kill your Cat. Cats do not fail that often unless there is lack of fuel control or the internal honeycombs break apart from time. I would make sure you check all of your systems are working correctly. Dont just bolt on a good Cat and kill it. I have seen more techs in the field diagnose P0430 code, not do there home work and throw $$$$ by killing a brand new Cat.

[PAULSPEED]

You should look for used cats.

There are used Porsche junk yard in Los Angles and Arkansas.

I am sure there must be Porsche junkyards in Germany.

Paul