In recent years, with the rapid development of science and technology, with the wide use of new materials, new technologies and new technologies, the design and manufacturing level of automobile has been greatly improved. The technology of auto failure detection and diagnosis is becoming more mature, and automobile maintenance technology is constantly updated. However, people's understanding is lagging behind the development of science and technology, and the remaining misunderstandings in automobile maintenance have a great influence. There are 10 main manifestations as follows: 1. the axle bush of the sliding bearing must be scraped. And modern cars, especially small engines, are thin and wear resistant alloy coatings on the crankshaft bearing and connecting rod bearing bearing bushes. They are not allowed to be scraped and can only be selected according to the corresponding size. If there is no suitable size of the crankshaft bearing, it is necessary to use the method of base hole grinding to obtain the proper fit clearance when necessary. 2. engine water temperature is afraid of high and low. In fact, the low temperature of the modern automobile engine is very low, which will make the combustion of mixed gas insufficient, the power is reduced, the fuel consumption is increased, and the lubrication is bad, and it will also cause the excessive emission. The 3. valve clearance is larger than the smaller one. In fact, the valve clearance is large, and the valve lift is not enough, which makes the intake volume insufficient or the exhaust is not smooth, which reduces the power of the engine. 4. oil is getting better. In fact, too much oil will do harm to the engine, especially the tilting engine and V engine. It increases the rotational resistance of the crankshaft and connecting rod, and increases the oil splashing to the cylinder wall, resulting in the increase of coke in the combustion chamber. So too much oil will reduce engine power, increase wear and tear, and also cause excessive emissions. The 5. air hub is not lubricated. It is considered that the wheel hub is filled with grease, which can ensure the lubrication of the hub bearing. The empty hub with grease coated on the bearing is not lubricated, and the gap between the center of the hub must be filled with grease. In fact, this not only wastes grease, but also affects the heat dissipation of bearings, which is harmful to the bearing lubrication. The 6. brake is good or bad to see that the wheel has been locked, and the modern car requires the wheels to be unlocked, so the anti lock device is specially installed. Once the wheel is locked, the steering of the car is out of order, the wheel is slippage, and it is easy to fail, so it is not the longer the longer the better. 7. small point of contact gap of broken electrical apparatus. In fact, the contact gap is too large and the contact closure time is short, which reduces the primary side current of the ignition coil and causes the high voltage spark to be weak, thus causing the engine to be difficult to start. 8. the ignition advance angle or injection advance angle is larger than the ignition angle. The deflagration of the engine will cause great damage to the piston, seriously affect its service life and increase the starting resistance of the engine. 9. fastening bolts are rather tight and not loose. As a matter of fact, the bolts of each part of the automobile have corresponding value according to their diameters, pitch and usage. It is not good to loose the bolts that can not reach the specified value, but the blind increase of tightening torque will make the fastened parts deformed, and cause the elongation of the screw, the deformation and even fracture of the thread. 10. when the car is maintained, it will be relieved if it is opened and checked. With the improvement of manufacturing level, the service life of modern automobile parts has been greatly extended. Random inspection and demolition will inevitably destroy the state of fit. In today's automobile failure detection technology is becoming more and more perfect today, if there is no obvious failure of components or assemblies, do not generally remove the inspection.