ST185 JDM engine and ECU. Maybe a couple years ago my st185 started experiencing this. The first start of the day it would start but I'd have to let it idle for 30-60 seconds or it would die when give it gas. After that drives and starts fine all day. Even after sitting at work for 9-10 hours. Next day is 50/50 but sitting more than a day it will always do it on the first start. It has gotten worse to now I have to crank the engine for 20 seconds or more till it starts barely firing till it is firing enough to idle on its own. In effect, the regular injectors are fighting to get the engine to idle good enough to drive because the cold start injector did not kick in. Then same thing have to let it idle for 30-60 till I can drive it. I have replaced fuel pump, filter, cold start switch/sensor, the cold start injector was removed and tested ok. And the coolant temp sensor was bad but a new one (green plug) didn't fix it.
Testing found that the cold start injector has power but no ground driver.
Further research, the ECU pin diagrams say that JDM ECU's don't have a cold start injector STJ pin but USDM ECU's do. So where does the cold start injector control come from on JDM? When working properly the cold start injector only sprays when the starter is cranking.