[Auto repair knowledge]Common causes of vehicle cold start idling jitter

Shaking of cars during cold start is a common problem with gasoline cars. The most fundamental reason for the jitter phenomenon of cold start or neutral gear is poor combustion in the cylinder. If the combustion is not good, the power provided by the car will not be enough, and the car will shake. As an example, suppose that the horse can pull the car with 100 points of force, but if it only uses 60 points of force, of course, it will not move and shake. When the ignition energy is low, the first problem that the car faces during cold start is the low temperature, the temperature in the engine is not enough, the fuel andlubricating oilThe temperature is not enough, so you should inject more fuel during cold start to meet the power requirements.Spark plugThe larger the gap, the smaller the ignition energy. The fuel atomization is not good at low temperature, and the fuel needs higher ignition energy. If the car is used for a long time, the ignition gap of the spark plug will easily become larger, which will cause the ignition energy to decrease, which will affect the dynamics and cause the car to shake. in addition,Ignition coilsAging, spark plugHigh-voltage lineAging or leakage can also lead to a reduction in ignition energy. Inappropriate mixing ratio The inaccurate adjustment of the oil-gas mixture ratio exists in both open-loop and closed-loop control. In a closed-loop controlled car,Oxygen SensorThe lowest operating temperature is 370 degrees Celsius. If you just start the car, becauseexhaust pipeThe temperature in the medium does not reach 370 degrees Celsius, so the oxygensensorNot working. At this time, the ECU made a mistake in its judgment, and errors occurred in the control of the oil and gas mixing and ignition timing through the actuator, which reduced the power output of the car and appeared jitter. 　　ValveAnd intake duct carbon deposits If carbon deposits occur in the valve and intake ducts of the engine, because the carbon deposits can absorb an appropriate amount of fuel (just like water flows through a river bank, the soil has to absorb water), the ECU judges that there is an error. The computer actually sprayed out 100 parts of oil and gas, but only 90 parts actually got into the cylinder (10 parts were absorbed by carbon deposits), so even if the remaining 90 parts of mixed oil and gas were fully burned, the required power would not be achieved. The phenomenon of jitter is inevitable. The working conditions of each cylinder are different Similarly, spark plugs of multi-cylinder engines have the above-mentioned problems. After a long time of use, the ignition gap and time control of the spark plug will be different, but the ECU cannot diagnose this deviation, and still treats "them" equally. This leads to actual and theoretical errors, and as a result, some cylinders produce If the power is too small, it will cause jitter.After the engine is used for a long time, each cylinder liner andpistonThe gap will also be different, that is, some gaps are large, and some gaps are small. During a cold start, there is no good oil lubrication, and a cylinder with a large gap is likely to leak a certain amount of high-temperature gas from the gap, thereby reducing the power output. Water temperaturesensorMalfunction If you have a fever, but the thermometer reading is normal, what will happen? The water temperature sensor is one of the important basis for the computer to judge the working condition of the engine at that time. If the temperature of the engine is minus 10 degrees Celsius when the engine is cold started, but the sensor "tells" the computer that the temperature is 20 degrees Celsius, then the computer will inject fuel at 20 degrees Celsius. Of course, the amount of fuel should be small, and the jitter is of course natural. . Other factors The air flow meter is dirty, which reduces the intake air volume; the EGR (exhaust gas recirculation) valve is not working well, and exhaust gas is introduced at idle speed;motorControl the bypass intake port to adjust the intake air volume. If the voltage is low, the work may not be in place; the oil product is too poor to reach the corresponding calorific value, resulting in low combustion power output. The above four factors can lead to poor combustion in a certain cylinder during cold start or when waiting in neutral, resulting in engine jitter. Related: ·The correct use of three-way catalytic converter[汽车修理常识]
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