My '99 New Beetle's catalytic converter is disintegrating after 79,000 miles. The "guts" of the converter are rattling badly at certain engine speeds (I have verified that the rattle is not loose exhaust shields), and the exhaust coming out of the tailpipe smells bad. Not like rotten eggs, but like raw exhaust. This has been going on for a number of months but the exhaust smell has only shown up in the past week or so.
Two days ago, the CEL came on. I assumed this probably had something to do with unconverted exhaust reaching the oxygen sensor downstream of the cat, but the code is P0171 - System Too Lean. This does not seem to fit with the cat self-destructing, unless maybe the guts have shifted so that the downstream O2 sensor is somehow blocked from sniffing the exhaust?
I'm trying to determine if I've actually got two problems, or only one!
Thanks from a newbie / lurker...