Is it normal for the pointer of the car tachometer to shake up and down?

If the pointer of the car tachometer shakes up and down, as long as the shaking amplitude is not very large, it is normal. Because the engine speed will not be very fine, the idle speed will not be a fixed value, it will be low and high, so don't worry too much; If the tachometer fluctuates greatly and the engine shakes, there is something wrong.

The reasons why the tachometer floats when the car is hot are the leakage of waste gas valve, the failure of spark plug, abnormal cylinder pressure and poor sealing effect of throttle valve. Once some aspects are abnormal, the engine will not work normally, and it is very likely that one or more cylinders will catch fire. It is recommended to check whether the throttle and spark plug are normal first, and then do a good job of cleaning.

When the car is cold, the tachometer will float. Considering that it is caused by carbon deposition in the intake system, it is suggested to check whether there is too much carbon deposition in the throttle, whether the oil pump and idle valve are faulty, and then take targeted measures. In addition, when the signal fed back by the water temperature sensor is disordered, it is easy to cause the tachometer to float slightly. At this time, check the water temperature sensor and repair it as soon as possible.