What is the reason for unstable idle after replacing spark plugs?

[LeHeidi]

The reason for unstable idle after replacing spark plugs is that the throttle is too dirty, causing inaccurate air intake. Spark plugs are mainly composed of a terminal nut, insulator, terminal stud, center electrode, side electrode, and shell. The main types of spark plugs are: standard spark plugs, projected insulator spark plugs, electrode spark plugs, seat spark plugs, pole spark plugs, and surface gap spark plugs. Spark plugs are installed on the side or top of the engine. In the early days, spark plugs were connected to the distributor via ignition cables. Over the past decade, most car engines have been modified to connect the ignition coil directly to the spark plug. Spark plug working principle: The spark plug's ground electrode is connected to the metal shell, which is screwed into the engine block via the cylinder head threads. The insulator mainly serves to isolate the metal shell and the center electrode. The terminal nut is the part of the spark plug that contacts the high-voltage coil. When current passes through the terminal nut and the center electrode, it breaks down the medium between the center electrode and the ground electrode to produce a spark, thereby igniting the air-fuel mixture in the cylinder.