hi all,
i had to do my 2 yearly smog to register my '87 740 wagon, and i just squeaked passed the maximum allowed NOx and CO readings. it literally was within the error of the machine, i'm sure. the question is, do you think it's the O2 sensor? catalytic converter? both? i know there isn't a way to tell without a proper diagnostic, but any guesses?

i should say that my volvo during cold morning starts (i.e. california winter morning) has better idling than summer morning starts. it also seems to "have more power" in winter than in summers. ofcourse, it's just a feeling. that kind of leads me to believe it maybe a o2 sensor... again, any ideas?
jun

p.s. i should say she's a non-turbo, b230.

Can't be the O2 sensor. If you were too lean, the CO would be low. Too rich, the NOx would be down. Can't adjust both by correcting the air/fuel ratio. Most likely the cat. How old is it? It is cheaper to replace it next time the test comes than to mess around paying for diagnostics.

i've owned her now for just over 2 years. i haven't replaced the cat, and i haven't seen any paperwork that says otherwise. how long do those things supposed to last anyways?

In normal use at least 5 years. older engines with oil burning, less. they can be had on line for about $140.