1700 ppm, 1273 is the max. my CO and HC were virtually nonexistant. I've changed the EGR valve and O2 Sensor. I have no codes in the computer. Is it worth it to change the Cat? Its about 5 years old, pepboys el-cheapo and the heatshield is falling off.

1986 2.8 V6.

 

Yes. The Cat was probably clogged by a bad O2 sensor. I replaced my cat a year ago. Within 9 months, my cat passed NOX by only 1 point. So I am swapping it out with a Catco when I install my Hooker Cat Back this weekend. I am also changing the o2 sensor, to prevent premature Cat failure.

Andy

 

Check and make sure your smog pump is working correctly.

I passed everything besides NOx without my pump even being on my motor.

 

Also, check for proper function of EGR valve.