[325spd]

(where it is/where it should be)
hydrocarbons(hc) 1.10/0.80
carbon monoxide(co) 23.74/12.00
oxides of nitrogen(nox) 2.05/2.00

new o2 sensor, i bought a factory exhaust that had an aftermarket cat on, prev. owner said about 10k on it so it shouldnt be bad. i wouldnt rule it out tho. any input is appreciated

[Dirty Red]

so your car must have been the exhaust I was smelling when you guys were in front of me. Your car is running very rich according to those carbon monoxide levels...

[325spd]

according to the mechanical advisor or whatever her title is there its running lean..

[Dirty Red]

Oh ok. I always thought high carbon monoxide levels meant it was running rich...

[325spd]

idk im lost too. i didnt think it was running that far off... it runs good tho if you ask me.

[bastardE38]

You are both right. Those numbers are confusing. HC's indicate slightly rich mixture. CO indicates incomplete burn of fuel. NOx indicates lean condition.

Causes of high HC: When combustion is incomplete because of too rich of a mixture, raw gas results in the exhaust. If a cylinder does not produce sufficient compression to burn the mixture, unburned HC's will exit the cylinder. Piston ring blowby. And of course when the igntion system does not provide adequate spark.

Causes of high CO: Rich condition. Uneven air-fuel distribution in the combustion chamber and too much quench from low cylinder wall temperature can also be the cause.