[john walker's workshop]

first, as you work the starter, the cold start valve sprays fuel into the intake, and if you have a decent ignition system, the car will fire fairly quickly. this doesn't mean it will continue to run, as all the CS valve does is get it firing. the warmup regulator takes over from there, and keeps the mixture richer for a few minutes until the engine warms up. the sputtering and popping when it's cold usually indicates that the WUR is a bit off and not richening the mixture like it should. i would first look into the cold start system, if you have to crank for 30 seconds before it will even fire. of course the points and plugs, and general tuneup specs need to be in decent order for best results. search "warmup regulator" or "WUR", for info on how to make it run richer.