Worrying about smog test results and very low local MPG (89 Integra)

If your oxygen sensor has never been replaced, I would not be surprised if it's worn out. That would explain both the emissions and the gas mileage..

You have unburned fuel or oil in the exhaust at idle.

Most commonly caused by an ignition misfire.

Any suggestion to correct the "ignition misfire"? Thanks!

=46irst you have to find out which cylinder(s) are misfiring. I'm not sure what type of equipment and experience you may have, so I won't go into specific diagnostics right now.

Replacing the spark plugs is quick and cheap. Also,with the mileage you have, I would agree that replacing the O2 sensor and PCV valve would be a good idea.

As I said, this is the most likely cause. There are others, but your readings don't indicate another fault.

If you have a misfire at idle, it should be relatively obvious. Does the engine seem to buck or vibrate abnormally? Also listen at the tailpipe for any irregular coughing or puffing noises from the exhaust indicating a miss.

~~~~~~~~~~~~~~~~~~~~~~~~~~ You are right. This did happen! I already changed spark plugs. What's my next step?

So are you saying that it did buck or vibrate and it doesn't now? Did changing the plugs make any difference?