What is the reason why the tachometer pointer shakes up and down?

Circuit system failure: It may be caused by the failure of the battery voltage sensor, or the loose pile head of the battery, or some automobile circuit system failures such as generator failure.

Spark plug failure: If the spark plug with more than one cylinder fails, it will easily lead to unstable idle speed. In view of this situation, it is necessary to clean the spark plug in time and replace it directly if necessary.

Too much carbon deposit in the engine: too much carbon deposit in the valve train of the engine, such as the throttle valve and the mixture combustion chamber, will affect the intake of the engine and the combustion of the mixture, resulting in premature combustion and deflagration, and will also cause the engine speed to be unstable.

Cause of Throttle Failure: If the throttle position sensor of the vehicle fails or the motor controlling the throttle fails, it will affect the throttle opening and fuel injection control, so it will also lead to unstable engine speed, which will be reflected in the tachometer.

Insufficient fuel supply or uneven air intake: when the tachometer pointer fluctuates up and down, it is likely to be caused by insufficient fuel supply or uneven air intake; This situation will directly affect the working performance of the engine, so at this time, the speed will rise and fall, and then the tachometer pointer will not fall back normally.