Hey everyone,
I just had my Amigo smogged, and it passed. But the numbers jumped up quite a bit since the last time it was smogged 2 years ago (30k miles). HC(ppm) has doubled, CO is up 0.1%, and NO(ppm) has trippled. Before the test, I replaced the spark plugs, distributor cap, and distributor rotor. The O2 sensor is 6 years (55k miles) old. If I remember correctly, it's a Bosch. I've also been running the Amigo with a bad mixture control valve; it backfires between shifts when cold.

Do you think it's just a bad O2 sensor or is there something bigger to be concerned about?

I'm worried that all the backfiring has damaged the catalytic converter. Is there a way to test this?

Below are the smog numbers. My amigo is stock except for the 31s.

2 years ago
test speed | HC(ppm) | CO(%) | NO(ppm)
15 mph | 58 | 0.09 | 227
25 mph | 43 | 0.11 | 226

this year:
test speed | HC(ppm) | CO(%) | NO(ppm)
15 mph | 100 | 0.19 | 634
25 mph | 79 | 0.22 | 574