1991 Honda CRX start problems

Engine Mechanical problem
1991 Honda CRX 4 cyl Front Wheel Drive Manual 249189 km's

hi, I drive a honda crx from 1991 it's a ED9 with a D16A9 in it (the DOHC non vtec engine) every time I want to start in the morning or when the engine is cold it doesnt go to it's 1900 rpm's first he stay's a bit around 200 to 300 rpm and then it goin great to 1900rpm and when my engine is hot I have no start problems, I have replaced the injectors, spark plugs, EAVC (on the back of the intake header), fuel filter, fuel pressure regulator, throttle body and nothing helps

can you help me please?
@ the official honda dealer they told me that it could be one of do's things but it isn't so what do you think?

greeting from belgium