hi. 800 CFM quadrajet. Newer style with the APT. The car runs rich at idle while in park or in gear. Choke adjustment is ok. Carb is basically new, but was prepped by SMI induction (including drilling the idle passages). If I screw the idle adjustment screws in the front of carb all the way in, car of course goes too lean and stumbles. If I just crack them open 1/4 each, car idles and comes off idle fine, but is rich according to my A/F meter (~12:1). Part throttle cruise is ok. Should I worry about about the fact the meter shows it is so rich at idle? I will be in a lot of stop and go traffic and would hate to foul plugs because of this. Suggestions of what to look at?
Contrary to popular belief, the front mixture screws do not adjust idle mixture, they meter the volume of fuel air mix allowed to enter the air stream. The actual fuel air idle mix is determined by the passages and idle air bleeds. My 800 Q-jet idles right about 13.3 according to my A/F meter.
If it runs well, check the plugs and see what it shows. A little rich is probably better than a little lean. You have a working PVC valve/system?
What quadrajet is it? Would need to know the idle tube size, down channel restrictions and idle bleed sizes you currently have.
it took a long time, but I've learned to ignore the A/F meter - go by your gut, plugs, tailpipe and sense of smell. tuning to perfect ratios never produced the best ET's, at least in my 65.
Most q-jets end up with the mixture screws several turns out from seated. If yours are than sensitive and nearly closed then there is a LOT of fuel coming down to them at idle speed. If you can't clean up the A/F at idle and it's still stinky and rich then you will need to either add some idle air or reduce the DCR's and maybe even the idle tubes size......Cliff
