Idle speed is unstable after overhaul, and it always goes up and down. What happened?

There are several reasons. 1 depends on the opening and closing degree of the intake throttle, so clean the lower throttle. 2. Overhaul the engine to see if the fuel injection is not smooth or blocked. Use the diagnostic computer to check the dynamic data of engine fuel injection and check the fault code. 3. Ignition conditions of spark plugs. After overhaul, there are many general faults, which need to be checked one by one. If the ignition condition of the spark plug is not good, it should be replaced. The main search points are intake, exhaust, ignition, fuel injection and clearing engine fault codes.