What is the reason for Bora's unstable idle speed?

Faw Bora) 1.8t car adopts four-cylinder multi-point injection and independent ignition coil for each cylinder. When the cylinder fails to work, the engine control unit can recognize the combustion interruption of the cylinder and store the fault code. For the combustion interruption fault, use the display groups 14, 15, 16 in the 08 function (reading the measurement data block) of the vag 1552 fault reader to query the number of misfires of a specific cylinder, and judge the fault according to the specific data. The data displayed in the third display area of the measurement data block display group 14 indicates the total number of misfires of each cylinder (specified value: 0~5 times); The data displayed in the 1, 2, and 3 display areas of the measurement data block display group 15 respectively represent the number of misfires of 1, 2, and 3 cylinders (specified value: 0); The data displayed in the 1 display area of the measurement data block display group 16 indicates the number of misfires of the fourth cylinder (specified value: 0). When the combustion interruption fault code appears, the fault may be caused by the failure of cylinder injector or the failure of cylinder ignition system. Such as spark plugs or ignition coils (Bora cars use independent ignition coils for each cylinder and there is no high-voltage line, so there is no high-voltage line fault). The fault code of this vehicle shows 1 cylinder combustion interruption. Because the car is a new car, it is unlikely that the spark plug and injector will fail, and the problem is probably the ignition coil.