2000 VW Jetta (MK4 - VR6) - Code P0420

[jagdato]

Went in to do my emissions testing today and failed with the code returned as P0420. Replaced sparked plugs in August '09...car runs fine with no rough idle.

Not sure what this means or what to do. The VWVortex forums say it could be 02 Sensors OR Cat. How do I know which it is I need to fix or if it's something completely different. Any ideas/recommendations to get it fixed and pass emissions?

[spastik]

Hey John.

One thing you might do, which is a cheap fix... get a spacer put on the o2 sensor. it makes it stick farther back so it gets smaller samples of the oxygen.

similar to this
http://www.energeticforum.com/renewable-energy/1387-o2-sensor-modification-using-spark-plug-non-foulers.html

[DubstepDave]

It's most likely the o2 sensor, which is a very common failure on these cars. Replace the o2 sensor, get the codes cleared at shucks, and go re-test. You should be fine.

[jagdato]

Thanks, fellas. Going to the mechanic for good measure...hopefully it's not the cat.

[cedge208]

Hey John.

One thing you might do, which is a cheap fix... get a spacer put on the o2 sensor. it makes it stick farther back so it gets smaller samples of the oxygen.

similar to this
http://www.energeticforum.com/renewable-energy/1387-o2-sensor-modification-using-spark-plug-non-foulers.html

I read through that whole thread and it looks like it doesn't actually work.. just all theory. Unless you did a bunch of other things to the a/f mixture and use combustion enhancers.

[InSepsis]

So we figured what the issue is (at least what mechanic says) and it's the Cat that is out.

The problem is that the mechanic wants 1100 for the parts + labor to replace it...

What do you guys think?

[CRIMES]

oem cats are expensive as hell

[RunninWild]

buy an aftermarket cat for 100 bucks and get it welded in at boise muffler for 30 bucks

[DubstepDave]

I seriously highly doubt it's the cat. But I agree with Curtis, get an aftermarket cat and have Boise Muffler weld it in.

I would really seriously suggest changing out the o2 sensor(s) first though.