cold start valve function is the enitial shot of fuel to start cold engine. once you start the warm up regulator can take up the slack in so far as running a richer mixture during cold engine warm up. (cold start enrichment). the cold start valve is run by the thermo time switch, this temp sensor regulates the time the cold start valve stays open or turns on at all. tha cold start enrichment sets a lower fuel control presure at the fuel distributor allowing injectors to run richer, as the engine heats and the electrical signal to the warm up regulator warms it, the control presure increases to lean the fuel system to run with the warmer temps. O2 sensor cars had another temp sensor that controled when the lambda seystem would start. alot of the sensors were set too warm and were allowed to work on a cold engine on a warm day. this caused hesitations and poor proformance. a bad cold start valve causes longer cranking time and no start at all in cold weather. a bad warm up regulator will give same complaints as o2 circut falty but lasts longer. a fuel presure guage is the best way to diagnose fuel issues on a cis system. a noid lite for bosch injection is also a good tool. on the electrical side the most common issue is either the thermo time switch or the power sorce. many times on these systems the power sourse is tied in as a secondary circut on a relay such as fuel pump or lambda relays. so part of the relay works and another doesnt, hard to find problem at times but not uncommon.