Why the EFI diesel engine is high and low when idling?

The reasons for idling fluctuation of EFI diesel vehicles are as follows: 1, there are too many dirty things in the throttle and intake port: too many dirty things will lead to the change of the cross-sectional area of the intake port, which will make the control unit unable to accurately control the intake, resulting in abnormal combustion of the mixture that is too rich or too thin. 2. Various gases enter the manifold: air, gasoline vapor and combustion waste gas that should not enter the manifold or various valves leak into the intake manifold, causing the mixture to be too rich or too thin and making the engine burn abnormally. 3. The control unit receives the wrong signal: it sends out the incorrect command, which leads to the inaccurate control of the engine idle intake, and the problem of the engine work is the cause of the unstable idle speed.