What is the reason for the slow idle speed of Guangzhou Automobile Chuanqi gs4 in D gear?

The reasons for the slow idle speed of Guangzhou Automobile Chuanqi gs4 are as follows:

1, the engine has serious carbon deposit, the throttle valve is too dirty or the injector has too much carbon deposit;

2, the ignition system problem, the ignition system is not easy to use, the spark plug is not very good;

3. The oil pressure is unstable;

4, engine parts aging.