CO2 adjustment screw on air mass meter...?
 

My 77 280z is running a little rough. I just moved from a city with an elevation of 3000 ft to a city at sea level. My service manual tells me that the adjustment screw on the drivers side of the air mass meter (facing the ignition coil) is the CO2 adjustment screw (altitude), however, it gives me instructions to use a CO2 meter, which I do not have. I was hoping someone could help me adjust the roughness in the rpm progression by using this screw adjustment and tuning by sound (engine running). Where do I start? How many turns out from all the way in do I begin, etc? Thanks, 77 280z

You went from thinner air to heavier air, you probably want to turn it in I would say about 1/2 turn and see how that does. You may also need to adjust the idle screw to keep the idle up. Don't mess with it too much and keep track of the changes you make. That screw is only good for idle mixture adjustments though. It's an air bypass around the AFM flap so it's not so much a CO2 adjustment as it is an idle air mixture adjustment.