My VW is reading cylinder misfire and catalytic converters below threshold, what do i do?

Question

2000 VW Passat GLX V6 Manual Transmission.

I replaced the Cats with used cats (b/c brand new they were way too expensive) but i'm still getting the check engine light error... and now i'm getting an error for cylinder misfire (#6). Is the cause of my problem likely the cats or the cylinder misfire? And why are VW's so expensive to repair?!

Answer 1

The misfire is causing the whole problem. The misfire will cause the cat to build up soot in it, and that is bad. You need to resolve the misfire issue, and run it for a while and let the cat get hot again, and it will take care of itself. The misfire will cause the converter to have raw fuel go into it, and will take some time to burn out, so just deal with the light for a day, and it will go away once you get it firing right. Check for a sticking injector, bad injector, bad wire or coil pack. The spark plug or wire may be bad and firing, but just not all the time. You must resolve the misfire, and don't worry about the cats, as this is the cause, this I'm sure of. You may have to clear the codes with a scan tool in order to get the light to go out, but after about 20 miles it will reset on its own, in most cases.
As for why are they so expensive to work on? If you will notice, there aren't that many of them on the road, and not that many technicians to go around, and even less that are VW trained. Supply and demand thing I guess.
I'm glad I could help you, Good Luck!!!

Answer 2

It is technically illegal to resell used cats. Now you know why. You don't have any means of testing them without a smog machine. If you buy a used alternator or starter, its quality is known immediately upon installation.
As for the miss-fire. it might be time for a tune-up, or perhaps you just have a bad plug wire.
Check the wires out with an ohm meter. Inspect the plug(s) for fouling and proper gap.
Check the Oxygen sensor that monitors the cat. If it is faulty, or if the heater doesn't provide enough heat, the voltage pattern will indicate an inefficient catalytic converter.
It may be more expensive than you want to deal with, but ALL converters are expensive, even the "Universal" units from the local muffler shop. They contain precious metals, like platinum, palladium and rhodium. None of these metals comes cheap.
If you are just at the point of throwing parts at the little car, stop it.
Either learn how to do the diagnostics first, THEN perform the proper repairs to the problem, not the symptom, or pay a reputable repair shop to do it for you. You will in the long run save much time, effort, frustration and money. Guaranteed.

Good Luck and Merry Christmas

Answer 3

My wifes beetle 2001 had the same codes.

I gave it a full tuneup with new platinum plugs, erased the codes and it has been fine since. Yes german cars can be expensive to fix, but feel lucky it is not an S class Mercedes. :)

Answer 4

Them German cars for you. Probably have to see if there is a programming problem with the computer, on the car. SOme have had to be reflashed to fix the cat probs.