General Category > Quadrajet Carb Talk and Tips
86 c20 4 bbl carb (failing smog high nox new cat)
77cruiser:
--- Quote from: 77cruiser on February 19, 2015, 06:50:27 AM ---If you back out the APT screw the cruise should get richer.
--- End quote ---
Have you tried adjusting it, or is it backed out already?
Cfrench192:
I backed out the APT. Its definitely running richer now. I backed it out all the way and threaded it in 1/2 turn. Big difference in the cruise circuit. I'm going in for smog tomorrow. I will post the results. The cruise circuit is running as low as 15.3 A/F on the freeway (80 mph). Before i turned the apt it was running 17.3. If this fails I have a later model calibration kit coming in this week.
Cfrench192:
I would also like to add that the distributor is hooked up to full manifold. It has a new distributor with a light spring and 1 medium spring. The test showed 03 btdc and passed the timing test. The total timing is at 32. should I change the advance curve? I am running a functional egr.
77cruiser:
I think advanced timing contributes to high NOX too, may have to change the curve. How much do they charge to smog it?
DieselPower:
I would think that with a fully and correctly functioning EGR, NOx would not be a problem. Have you gone through any procedures to make sure that the EGR valve, solenoid, and associated wiring and vacuum are working 100%
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