What can I check or replace before I take to a shop[. thanks

 

Did you give it a normal tune-up yet? Plugs, cap, rotor, oil change and air filter. It's best to change the oil after a long drive to remove as much engine gunk as possible. Maybe spray a little carb cleaner in the carburetor. Also, clean the pcv valve by shooting carb cleaner in and shaking it (pulled from the valve cover, of course). If that doesn't do it, I'd suspect the catalytic converter. I'm glad I don't have to get a smog check.

 

As gsp4life suggests this is the least you can do before a smog test.
You should post the test results also.

 

Also, do this: Adjust the valves and then get it timed to factory specs (even a couple degrees off will change emissions numbers).

 

Thanks for the reply, yes I changed the plugs, rotor and dist. cap. I didn't think about the pvc valve being dirty, i'll do that next. I was wondering about the O2 sensors also.

 

You only have 1 o2 sensor on the manifold. If you suspect it's bad replace it, but use a denso 234-1051 or 234-1056 (I forget the difference I think one has a longer wire), and not a Bosch.

 

25 MPH RPM-2841, %CO2-13.6, %02-0.0, HC (PPM)-22, CO (%) MAX 1.32--MEAS-2.08, NO (PPM)-6---Failed CO (%)