What is the reason for the unstable idle speed in Britain and finidi?

Engine idling instability will be caused by mechanical failures of intake system, fuel system, ignition system and engine. Therefore, it is a wide-ranging and difficult job to diagnose the cause of engine idling instability, and it is not appropriate to replace parts easily. There are many reasons for unstable idle speed, so we should make a correct judgment according to the test results, theoretical analysis and maintenance experience.