Ok so i just got a 89 honda civic and it will not pass emissions. It idles rough. blows a bit of black smoke. it does have a hole in the exhaust somewhere cause all the sound is under the car. I did the usual tune up. It has a short intake so idk if thats making it worse or what but I NEED HELP!! Don't no what to do next.

 

What codes is the ECU throwing?

How was the car running before the tuneup?

What was done for the tuneup?
-change plugs (or minimum, check and set plug gap)
-adjust valve clearances
-check spark plug wire resistance
-check and set timing
-check and clean all ground points (body, transmission, thermostat body, valve cover); replace any bad ground wires. (a bad ground can cause all kinds of bogus problems)
-clean battery terminals
-replace air filter
-change oil and oil filter

-how old is the O2 sensor?
-how old is the catalytic converter?

 

I did most of that and it didnt pass. But then i checked the PCV valve and it was clogged so i changed that and it passed with flying colors. Thanks though