Guys, who knows how to analyze vehicle breakdowns?

How to analyze vehicle failures.

Looking at the condition of the car from the exhaust gas From the color and state of the exhaust gas, you can grasp the quality of the operation of the automobile engine. After the vehicle is slightly warmed up in a cold start, if the exhaust pipe has not been modified, most of the vehicles with normal engine operation, the exhaust pipe will spray some colorless water, and after driving for a period of time, the drainage will disappear, and the tail end of the exhaust pipe should also be clean and free of carbon deposits. If the exhaust gas discharged from the exhaust pipe is still white after the car is warmed up, it means that the car has lubricating oil entering the combustion chamber for combustion, which is a phenomenon of burning lubricating oil and must be sent to the repair shop for maintenance.

This problem can occur not only in old cars, but also in new cars, if the new car adds too much lubricating oil beyond the marking line, it will also cause too much lubricating oil to enter the combustion chamber and burn and produce white exhaust. However, it should be noted that if the exhaust pipe emits white smoke when it is just on the road in cold weather, it may be the result of water vapor condensation, and it should not be mistaken, but it is not normal for the exhaust pipe to still emit white smoke after the engine reaches the normal operating temperature (80-90 degrees Celsius). If the exhaust fumes emitted by the car are black, it means that the gasoline mixing ratio is too strong.

In addition to polluting the air, the gasoline mixing ratio is too strong, and it must be adjusted as soon as possible, as it is accompanied by consequences such as fuel consumption, weak acceleration and easy carbon build-up inside the engine. If it smells pungent, it may be that the carbon monoxide value of the engine is not adjusted properly, and it is best to check it with an instrument. In addition, stolen or poor quality lubricating oil, clogged air filters, worn or broken piston rings can make the exhaust fumes of the car black.

1.There are wearing parts in the car design, it is impossible to achieve all the parts on the car have the same life, some parts of the car itself are wearing parts, such as air filter core, spark plugs, engine oil, etc., the service life is short, and they need to be replaced regularly, if the dust is not replaced in time or the car is damaged in advance, it will fail. 2.

The quality difference of the parts themselves is carried by large quantities and produced by different manufacturers, and there are inevitably quality differences. There will be problems in the use of original parts, and there will be problems when the cooperative factory and unqualified parts are installed on the car, so all automobile manufacturers are working hard to improve the quality of parts and eliminate the quality defects of the parts themselves. 3.

The quality difference of automobile consumables The consumables on the car mainly include fuel and lubricating oil, etc., and the poor quality of these additives will seriously affect the performance and service life of the car, making the car more prone to failure. The addition of these supplies is often difficult to ensure by the user, a little attention will be added to inferior gasoline and inferior lubricating oil, which is extremely harmful to the car and the engine, and the user may not care, the car will have problems. 4.

The environment of car use is affected by the fact that the car is used in the open air, and the environmental impact is large. The highway road surface is wide and flat, and the speed of the car is high, which is prone to breakdowns and accidents; The roads are uneven, the car vibrates and bumps severely, and it is susceptible to injury. The large power consumption in the blind area of Shanbi and the long waiting time in the city have made great changes in the working conditions of the car, and sometimes when it cannot be adapted, it is easy to break down or cause sudden damage.

Fault diagnosis: check the vehicle, and find that when the car is cold, the engine starts with a "click" sound, and there is no abnormal sound when the engine is turned off and started immediately. When the engine accelerates to 3000r min, a rhythmic "click" sound is heard inside the engine, and the sound disappears when accelerating to 3500r min or 2500r min.

Test drive, abnormal noise appears in 5th gear at 80km h, and the abnormal sound of acceleration or deceleration disappears. First of all, use IT-2 to check the fault code, the vehicle has no fault code, and the control system is normal. The cylinder breaking experiment was done, and the abnormal noise did not change.

Checking the vehicle with a stethoscope reveals that the abnormal noise is coming from the front of the engine, near the timing cover. Remove the valve cover and check that the timing chain is not abnormal. Since the squeak is most pronounced at around 3000 R min, this speed is exactly where the low-to-high conversion of the engine from VVT-I comes into play.

The first cam bearing was removed and the filter element was checked, and no problems were found. No abnormalities were found in the camshaft sprockets and timing chains. Only the crankshaft sprocket was not checked, and the owner did not agree to disassemble the timing cover, and was ready to remove the crankshaft position sensor and check the crankshaft sprocket with a flashlight and lenses.

A problem was discovered when the crankshaft position sensor was removed, with broken crankshaft teeth sticking to the magnetic position at the front of the sensor. At this time, it was basically concluded that the problem was in the ignition timing part of the engine, and it was found that the crankshaft sprocket was damaged, and the chain and other accessories were worn.

Troubleshooting: The reason for the abnormal noise is that the chain resistance increases when the VVT-I is running, and the abnormal linkage with the crankshaft sprocket causes abnormal noise. But why are the sprocket teeth of the crankshaft broken?

The author and the relevant maintenance technicians suggested replacing the engine crankshaft, sprocket, chain, VVT-i actuator, crankshaft sensor sprocket, oil pump sprocket, oil pump chain and other accessories. After the replacement, the abnormal sound of the engine cold start disappears.

Fault summary: It can be seen from the troubleshooting of the car that the root cause of the fault is the damage of the crankshaft sprocket, the wear of the chain and other accessories, and the abnormal sound of the cold car. When there is a problem, the IT-2 data flow is not checked, and if the VVT-i turns on the angle data flow during abnormal noise, the fault point can be found relatively quickly.

I hope the subject and netizens are grateful.

1. The car water temperature warning light turns off automatically after being on for a while, what is the reason for this?

Reason: If this situation occurs, it is first recommended to check whether the antifreeze is a loss of beam die, and if there is a lack of antifreeze in the water tank, it should be added to the normal liquid level immediately. Secondly, the antifreeze will have a certain amount of natural wear and tear, but it will not be too bad.

If you find that you need to add it frequently in a short period of time, then you need to check the water tank, water pipes, water kettle and warm air tank to check for leaks.

Second, when the car is running at high speed, the speed has reached 150 kilometers per hour, but the oil is not timely, and the speed has been more than 4,000 rpm, what is the reason for this?

Reason: When the hydraulic solenoid valve fails, the automatic transmission will enter the slope mode, which will force the third gear to drive, this change fault is a pressure regulation failure, you need to go to the store to check in time, first change the transmission oil to try, if the oil will be locked in the third gear position after the oil change, then you need to replace the solenoid valve.

3. By car'Sometimes, I always feel that the car is not enough cooling, should I add refrigerant?

Causes: Most of the causes of refrigerant deficiency are due to micro-leakage of refrigerant in the system. If the refrigerant in the air conditioning system is insufficient, the refrigerant injected into the evaporator from the expansion valve will inevitably decrease, and when the refrigerant evaporates in the evaporator, the heat absorbed will also decrease, and the cooling capacity will also decrease.

It is recommended to go to a 4S shop or repair shop for inspection first, if the inspection result says that you don't need to add it, you don't need to add it, because too much refrigerant is not good.