China Naming Network - Ziwei knowledge - In 2003, the idle speed of Futian scenery surfing was unstable, and the car shook at low speed. The throttle idle motor, atmospheric pressure sensor, ignition coil, ignition wire and nozzle were replaced. ...

In 2003, the idle speed of Futian scenery surfing was unstable, and the car shook at low speed. The throttle idle motor, atmospheric pressure sensor, ignition coil, ignition wire and nozzle were replaced. ...

Jitter during cold start is a common problem of gasoline vehicles. The most fundamental reason of cold start or neutral waiting jitter is poor combustion in the cylinder. If the combustion is not good, the power provided by the car is not enough, and the car will shake. For example, suppose a pony can pull a cart with a force of 100 minutes, but if it only takes 60 minutes, it will definitely not walk or shake.

Low ignition energy

The first problem that the car faces in cold start is low temperature. The temperature in the engine is not enough, and the temperature of fuel and lubricating oil is not enough, so more fuel should be sprayed during cold start to meet the power requirements. The larger the gap between spark plugs, the smaller the ignition energy. Fuel atomization is not good at low temperature, and fuel needs high ignition energy. When the automobile is used for a long time, the ignition gap of the spark plug is easy to become larger, which leads to the decrease of ignition energy, thus affecting the power performance and making the automobile shake.

In addition, the aging of ignition coil, aging of spark plug high voltage line or leakage will also lead to the decrease of ignition energy.

The mixing ratio is not suitable.

There is an incorrect oil-gas mixture ratio in both open-loop and closed-loop control. In a closed-loop controlled car, the minimum working temperature of the oxygen sensor is 370℃. If the car has just started, the oxygen sensor will not work because the temperature in the exhaust pipe is lower than 370℃. At this time, the ECU made a mistake in judgment, and the actuator made a mistake in controlling the oil-gas mixing and ignition time, thus reducing the power output of the automobile and causing jitter.

Carbon deposition on valves and air intakes

If there is carbon deposit in the valve and air intake of the engine, ECU will make a wrong judgment, because carbon deposit can absorb a proper amount of fuel (just as water flows through the river bank and soil absorbs water).

The actual control of the computer spewed out the supposed 100 oil and gas, but only 90 oil and gas actually entered the cylinder (10 was absorbed by carbon deposit), so even if the remaining 90 mixed oil and gas were fully burned, the required power could not be achieved, and the jitter phenomenon was inevitable.

The working conditions of each cylinder are different.

Similarly, the spark plugs of multi-cylinder machines will also have the above problems. After long-term use, the ignition gap and time control of spark plug will be different, but ECU can't diagnose this deviation and still treat it equally, which leads to practical and theoretical errors. As a result, some cylinders generate small power, which will lead to jitter.

After the engine is used for a long time, the gap between each cylinder liner and piston will be different, that is, some gaps are large and some gaps are small. In cold start, without good oil lubrication, the cylinder with large gap is easy to leak some high-temperature gas from the gap, thus reducing power output.

Water temperature sensor failure

What if I have a fever, but the thermometer reading is normal? The water temperature sensor is one of the important bases for the computer to judge the working condition of the engine at that time. If the temperature of the engine is-10℃ when it is cold started, but the sensor "tells" the computer that the temperature is 20℃ now, then the computer will inject fuel at 20℃, and the amount of oil is of course small, so it is natural to have jitter.

Other factors

The air flow meter is dirty, resulting in a decrease in air intake; EGR (exhaust gas recirculation) valve is not working well, and exhaust gas is introduced at idle speed; The idle motor controls the bypass air inlet to adjust the air inlet. If the voltage is low, it may not be working properly. The oil product is too poor to reach the corresponding calorific value, resulting in low combustion output power. The above four factors will lead to poor cylinder combustion during cold start or neutral waiting, which will lead to engine jitter.