High NOx and CO reading

I just failed my emission test with high NOx and CO readings on a 1994
Accord. Does anyone have any advice as to what could be causing this high
readings.

Thanks
Alex

 

That is an odd combo. Timing and mixture factors usually raise one while
lowering the other.

My suspicion is that the catalytic converter is kaput - assuming it is a 3
stage cat. It is a common cause of high NOx and can certainly produce high
CO by virtue of not breaking each of those down. I mention about the 3-stage
cat because the third stage - when used - is to break down NOx.

Basically, NOx comes from advanced ignition or lean mixture, while CO comes
from rich mixture.

Mike

 

egr ports are plugged, have to slide hammer out the plugs, clean
the ports and replug.
the egr system is in place to reduce nox, which is caused by
pressure and high temps.
Chip

 

Although that doesn't explain the CO. Still, EGR is cheaper than a cat!

Mike

 

CO is high, could be an inoperative O2 sensor. NOx is high, could
be an inoperative EGR valve, carbon deposits, over advanced timing,
cooling system too hot, lean mixture, cat-converter, or any mixture of
the above. An inoperative O2 sensor could have worn out the cat-
converter.