Sorry newbie question...Having slightly, very slight higher than normal CO2 readin,gs after taking a local emmissions test...apparently CO2 is created when there is a lack of air ....so can i not just adjust the mix adding slightly more air to ny using /adjusting the little screw that controls this? I fso how will i know which way is doing what. Adjust/turning it one way will rev up the idle -is this then adding more air to the mix is the opposite going to happen if i turn it the other way? (more air added then-higher the revs/idle speed - and less air gets mixed then lower rev/idle speed?)

 

bump for that....

 

I think what you are describing is the Idle Air screw. All it does is set the base idle speed. Your higher CO2 readings as you discovered are from a lack of air, or unburned fuel. The O2 sensor is what primarily controls the air/fuel ratio. I would investigate that first. Then, spark plugs, ignition components, air filter, timing, and what the heck, PCV valve. Also, make sure your thermostat is allowing the engine to reach the designed operating temperature.

 

OK Thanks i will try that