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There are 3 common failures of cold car in winter: cold car is not easy to start, engine idle jitter of cold car and bad speed of cold car, many maintenance personnel do not know how to get down when encountering these faults. Below we analyze and solve the 3 kinds of "cold car" fault. In the standard of vehicle repair, it is stipulated that when the ambient temperature is above -5 C, 5S should be used at most 3 times, and the engine should be activated at most. With the increase of current automotive technology, many users have no recognition of this standard. They want to use the starter in 5S to be successful, and the modern electronic control engines can do it. If the engine has a difficult starting fault, the cause of the failure generally includes the starting system failure, such as the battery power shortage, the starter damage or the starter circuit failure. Engine mechanical failure, such as gas leakage in the intake pipe, poor sealing between piston and cylinder, and tight valve closing cause low cylinder pressure. Too much Coke in the back of the intake valve and intake pipe causes the injected gasoline to be adsorbed by carbon deposition and can not enter the combustion chamber. Engine management system faults such as speed sensor signal is weak, water temperature signal is incorrect, and line contact is not good. There are faults in the ignition system, such as too much spark plug carbon or incorrect space, leakage of high voltage line and damage of ignition coil. Failure of fuel supply system, such as insufficient pressure of fuel system, leakage or blockage of injector. When the engine cold car starts, if there is no fast idle speed or unstable speed failure of the engine, the cause of the fault generally includes: engine mechanical failure, such as low cylinder pressure. Failure of the intake system, such as air inlet, air leakage, etc. There is too much carbon in the back and intake pipe of the inlet valve. Engine management system failure, such as water temperature, intake temperature signal is incorrect, line failure. There are faults in the ignition system, such as too much spark plug carbon or incorrect space, leakage of high voltage line, distributor cover, and damage of ignition coil. Failure of fuel supply system, such as too much carbon in the fuel injector, causes the fuel injector to be closed or blocked. Although many automobile manufacturers show that the cold car can start without preheating after the start of the cold car, the author thinks that the engine will be a little preheating 3 - 5min after the start of the engine, which will be of great benefit to the engine. Because this can reduce the engine's mechanical wear, for small displacement engine can make enough start power. If the cold car is started quickly, there will be a slight rush of car phenomenon, if the phenomenon of breaking a car is serious, the cause of the failure is generally: engine mechanical failure, such as low cylinder pressure causing engine power decline, more prominent in the cold car state, too much Coke in the back and intake pipe of the inlet, causing the injection of gasoline to be absorbed by carbon. Attached but can not enter the combustion chamber; engine management system failures, such as water temperature, inaccurate intake temperature signal, line fault, and so on; ignition system is malfunction, such as excessive spark plug charcoal or incorrect clearance, high pressure line, distributor cap leakage, ignition coil damage and so on; oil supply system malfunction, such as the internal glide in the injector. Too much carbon causes fuel injector to be closed or blocked. The diagnosis of the above 3 faults should be followed by the principle of the first electric machine and the first simple back propagation. If the engine is not easy to start, the hot car idling and the bad acceleration of the hot car, the "three heat fault" should be eliminated first. The diagnostic steps are as follows: check the appearance of the engine, check whether the vacuum tube and harness plug have any shedding, whether there is leakage, leakage, leakage and leakage. Use fault diagnostics to query fault codes and data streams. Use the multimeter, the oscilloscope and other equipment to carry on the measurement. According to the above inspection, identify the cause of failure and parts, repair or replace parts. After troubleshooting, the above equipment is used again to detect and reproduce the condition of failure to carry out tests or road tests. The reason for the "three cold" fault of the EFI vehicle is due to too much Coke in the intake valve and intake pipe, and too much impurity inside the fuel injector. If the above 3 kinds of faults occur on a new car, such as a car with a mileage of 60 thousand kilometers, it is suggested that the user do not clean the engine when the vehicle runs 20 thousand to 30 thousand kilometers. It is necessary to pay attention to the 2 items of "dialysis" and "dripping", because the former is good for cleaning the injector and the latter is cleaned. The effect of carbon accumulation on the back of the valve is good. The discharge of the bottle should be controlled well, the cleaning time should be controlled in 20 - 30 points, and some cleaning agents can be inhaled at the idle speed, and the cleaning machine is closed to increase the speed to burn off a softened layer of carbon. The proportion of dialysis detergent and gasoline is 1:5, poor cleaning ability is too thin, too thick will cause waste. In addition, the engine should run more than 20km at a higher speed (above 80km/h) after the removal of the free cleaning, so that the dissolved gelatin and Coke will burn from the tail gas at high temperature. If the vehicle is removed from the second day morning after dismantling, it will make the valve dissolve colloid, the starting more difficult and the engine idle speed more jitter, that is commonly known as the "sticky valve" phenomenon. Once this phenomenon occurs, it is necessary to remove it again.