Fault diagnosis: check and analyze the upper body of the blowout intake manifold, crack the upper part of the 4 cylinder and the lower part of the 1 and 2 cylinder inlet, and deduce that the air flow impact caused by the recombustion of the mixture gas will lead to the tempering when the inlet valve of the cylinder is in the non closed position. There are roughly five possible reasons for the analysis of the causes of tempering: (1) the intake gate card is stagnant in the non closed position, and the common is the carbon accumulation, the valve glial and the valve spring repositioning. (2) during the work stroke, after the mixture is ignited, the high pressure passes through the opening clearance of the intake valve to impact the intake manifold. 3. Ignition timing error. (4) too thin mixture leads to slow combustion and burning again. Poor oil quality causes incomplete combustion and reburning. After using the V. A. G1551 check to confirm the fault free code storage, first remove the intake manifold upper body, find the 4 cylinder inlet valve in the maximum open state, slowly push the vehicle, observed that the 4 cylinder inlet valve is also slowly closed. It can be seen that the intake valve return is good, not the valve assembly block failure. Further observation of the intake port in the 4 cylinder head covers no carbon deposition. Because carbon deposition and colloid formation generally take a certain amount of time, the vehicle can eliminate the possibility of carbon dioxide or gum causing stagnation of intake valve. Continue to slowly move the vehicle. When the cover of the camshaft is straight, the mark is aligned to check the timing mark on the lower crankshaft pulley. Because the ignition timing and the advance angle are controlled by the burr electronic ignition, it is considered that there is no problem in the timing of gas distribution or ignition in the condition of no fault code storage and ignition. At this point, the initial diagnosis is caused by the reburning of the mixture. One may be due to the poor cold atomization of gasoline and the slow combustion of mixed gas. In the case of severe mixture of gas, the combustion process may be dragged to the intake stroke of the next cycle. At this time, the remaining flame in the cylinder will ignite the expansion in the intake port, and the expansive gas may impact the intake manifold. However, in order to improve the combustion status, the control unit itself has made necessary amendments to this situation, such as instant thickening, and the possibility of air leakage and injector blockage of the intake manifold is not possible, so the possibility of reburning can not be found. It should be said that under the condition of normal evaporation of oil quality, this possibility is not large. The other possibility is that the incomplete combustion is ignited again, which is related to the ignition mode of the Bora car. A double spark ignition coil is used in the car, that is, the spark plug of two cylinders is ignited in series at the same time. When a cylinder is ignited at the stop point on the compression stroke, the other cylinder is at the top of the exhaust stroke at the same time. Under normal conditions, the waste fire is ignited in the exhaust stroke, but if there are a large number of incomplete combustion products in the exhaust stroke, the combustible mixture will ignite the expansion, which happens to be in the overlap angle of the intake and exhaust, and it is unavoidable to burst the intake manifold. Under normal circumstances, only a large number of unburned materials will lead to such a situation. Does this car produce a large number of unflammable materials? We further verify that the spark plug is removed, and it is found that the spark plug center electrode and the side electrode are completely soaked with unburned gasoline, and the insulator skirt is covered with a layer of black carbon, which is obviously abnormal in the new car less than a week, enough to indicate that the high pressure fire does not burn off the unburned gasoline, because 4 There are all such phenomena in the cylinder. The analysis of the damage of the components of the ignition system or the damage of the body parts is not very important. The pressure of the 4 cylinders is all 1400kPa, and the 4 spark plugs are all in order. In conclusion, in the end, only the oil quality problems, after asking the driver to know that the driver bought the car directly after the 25L 97 gasoline, then basically no train, until a week after the start of the car started to burst the phenomenon, extracting part of the gasoline, obviously still smell. We may as well combine the characteristics of cold start to analyze this problem again, when cold start, the coolant temperature is low, the starting speed is very low, only about 100r/min, so the effect of gasoline atomization is the worst, a considerable part of the oil particle state, at this time, the car press a large number of fuel injection according to the starting program, imagine the driver added 97 oil itself ignition point. For the high, and the difference in evaporation resulting from the poor oil quality, the natural unburned fuel is ignited at the end of the exhaust, which eventually causes the upper body of the intake manifold to crack. In order to avoid the problem of oil quality again causing the intake manifold to crack, when we replace the intake manifold, the air filter does not always enter the air inlet, and the accelerator pedal will be stepped on the ignition gear to the end, the opening of the air valve is maximum, then the vehicle is started, and at the same time, at the entrance of the throttle, the crisp "wheeze" appears at the same time. "Voice, after the vehicle warm-up, fire test again, everything is normal. Troubleshooting: reinjection of regular brand gasoline No. 93 of 30L, after a few consecutive morning start test, everything is normal.