gratuitous

I just had to get my car emissions tested again. Here in CO it's every other year for cars like my '99 Maxima. Anyway, within the last two years the HC emissions have quadrupled, the CO emissions have doubled, and the NOx emissions have quadrupled. CO2 is actually down. These readings are still way under the limits, and no check engine light has come on, but I believe that this all points to the fact that either my pre-cat, rear cat, or both are starting to fail. Right?

After doing a search and reading some posts, it seems as though I won't be able to determine which of the catalytic converters are failing unless I have an error code. However, it also seems as though the pre-cat is usually the first to go. Is this true? I've been looking at some aftermarket converters on pro.nissanpartspro.com, and they seem reasonably priced. Is it worth just getting under there an replacing the darn thing before the check engine light comes on? It sounds like it's not too difficult unless the bolts are rusted out? Thoughts?

'99 GXE with 116K

Thanks!

gratuitous

You know... the more I look into this, I think that the cats cooled down when the dude who was supposed to be running my test disappeared for 15 minutes to go take a break with my car on sitting there on the rollers and not running. The cats probably weren't operating at 100 efficiency because they had cooled down. That's my theory anyway.