First, it may be that the engine has serious carbon deposition, which is the most common reason for car jitter. When there is too much carbon deposit in the engine, the gasoline sprayed by the fuel injection head will be absorbed by the carbon deposit during cold start, which leads to the lean mixture during cold start and makes it difficult to start. In this case, only when the gasoline adsorbed by carbon deposits is saturated, it is easy to run into the car. After running into the car, the gasoline adsorbed on carbon deposits will be sucked into the cylinder by the vacuum suction of the engine for combustion, which will thicken the mixture and dilute the combustible mixture of the engine, resulting in idling jitter after cold start. The lower the temperature, the more oil is needed for cold start, and the existence of carbon deposit will affect the smooth start.

Second, there may be something wrong with the ignition system. Check the working conditions of spark plugs, high-voltage lines and ignition coils. The ignition system is not easy to use, and the spark plug is not in good condition, which will also lead to this failure.

Third, it may be caused by unstable oil pressure. If you clean up the engine carbon deposit, clean the throttle, change the oil pad and spark plug, etc. You still find the car body shaking at idle speed. I suggest you go to the 4S shop to check whether the oil supply pressure and intake pressure sensors are normal. If the oil supply pressure of the oil pump is abnormal, or the value of the intake pressure sensor is incorrect and the work is not good, the body will shake.

Fourthly, the car jitter is also related to the aging of engine feet. The engine foot is actually the damping system of the engine. The engine foot is responsible for absorbing slight vibration when the engine is running. If there is something wrong with the engine foot, these vibrations will be transmitted to the steering wheel and cab, causing idling jitter.

Five, it may also be caused by tire failure, which is divided into two aspects:

1. It may be that the condition of wheel balance is not good, and the owner needs to do a four-wheel positioning and dynamic balance as soon as possible. If the vehicle does not run off, tire dynamic balance can be done. ?

2. It may be caused by the deformation of the steel ring, which generally appears on vehicles with a long service life. Generally, wheel balance should be done when replacing new tires and rims, otherwise the steering wheel will shake easily when the counterweight is uneven. Body shake will affect driving comfort and handling judgment.

Extended data

1. Observe the shaking degree of engine cylinder block, and also observe the shaking degree of dipstick handle. The smooth dipstick handle is very clear, and the shaking dipstick handle looks double.

2. Observe or read the data block from the engine tachometer, and the speed fluctuates near the expected idle speed or violently at the expected idle speed side. The expected idle speed in the program includes standard idle speed value and load idle speed value (light on, automatic transmission in gear, etc.). ), air conditioning idle speed value, warm car idle speed value.

3. Start the engine in situ, and sit in the seat and feel the body shaking violently.

References:

Baidu Encyclopedia-Engine idling instability