azhari,

did you make any adjustments to the mixture before you develop these symptoms or did the fault appear spontaneously?

check the following.

plugs,

spark plug leads,

rotor,

distributor cap.

cold start valve-may be it continues to spray extra fuel even when your car has warmed up-hence the the uneven idle and rich mixture.-try unplugging the connector when the the car is warm. it is located on the fuel rail near the injectors ,has a bluish connector on my car ,so yours should be similar.

mine is a 1993,1.8 litre fuel injected and with a cat and hence an o2 sensor.

my gut reaction is a sensor of some sort is malfunctionoing-do you have acess to a fault code analyser to plug into the diagnostic plug in the engine compartment

hope you get a result