My first job was at Carter Carburetor in St. Louis from 1967 to 1972. Carter did development and manufacturing of Quadrajets under license from GM/Rochester. Soak the choke coil assembly in a 70°F water bath for about 15 minutes. Use a thermometer in the water bath. Then quickly take it out of the water and put it in place on the carb, forget the screws. Turn it so the choke plate JUST closes. The center mark etched on the choke coil housing should be pretty close to the pointer. If it is, take it off, dry out the water and mount it back on the carb in the same position; this time use the screws. If the index pointer is more than about 10 angular degrees from the etched mark on the coil, you probably need a new coil assembly. Then check the vacuum choke pull off by applying vacuum and then sealing the hose. If it does not stay retracted when you seal off the vacuum hose, it's bad. Fast idle should be around 1500 RPM on the top step of the fast idle cam with the engine warm. If you are experiencing lean coughs, or die outs after cold start up. Turn the coil one notch richer. If that doesn't relieve the lean condition on the next cold start, bend the little u-shaped link from the choke pull off to make it SLIGHTLY longer, so it does not pull the choke open as much as it did. That particular adjustment is very sensitive so adjust in tiny increments. Q-Jets were calibrated for low exhaust emissions so the choke will have completed everything it is designed to do within about the first 1.5 miles. After that first mile and a half drivability is often a bit weak until the engine is fully warm so cut it a little slack there. If you describe just how the car behaves after being cold started, and within that first mile and a half, it can help with the diagnosis.
