1991 240sx: Failed Smog- high HC and CO

[vancouverbc]

High HC(489 ppm) and CO(9.99%). Nitrogen Oxide was the best in 5 years.(similar results on both driving and idle test). They said the CO was the worst they have seen.

I recently installed a new catlytic converter. Had my distributor out and timed it to about 25 before top dead center because it idled better at that position. no check engine codes.

[the converted]

Sounds like your running rich and your timing is too advanced. What do you have done to the car?

[vancouverbc]

My o2 sensor was unplugged. I'm getting blinking light now indcating optimal mix. Mystified why I fail at idle because o2 sensor is ignored during idle as far as I know.

I have only removed the timing chain guides. I will retard timing. thanks.

[the converted]

when you unplug the O2 sensor, the engine goes rich. What blinking light are you talking about?

[liquid_cool]

i allways do the $100. buck smogg..you never fail!

[vancouverbc]

No, the O2 sensor was mistakenly unplugged. The connection was wrapped in tape so I didnt realize it. Once I plugged the O2 sensor back in, the O2 diagnostics in mode 2 said the mix was optimal. I know from the past that an unplugged O2 sensor does not trigger code. I'm just puzzled that I am failing the idle test because O2 sensor is ignored during idle.

[desertdustr]

For sure, retard timing,...What's your fuel pressure ??

[GIJOE69]

i say get a new cat & seafoam it and change out the plugs full tune up