案例：
輛汽車因發動機故障警告燈點亮進廠維修，經過檢查，發動機還伴有起動困難、加速無力以及急速熄火等故障。測量缸壓，多個氣缸的壓力均低於標準值，綜合判斷是發動機內部問題，於是解體發動機。
從拆解的情況來看，有些氣門杆已經彎曲，氣門上堆積了大量積碳，缸壁也有拉傷的痕跡。氣門杆彎曲會導致氣門關閉不嚴，氣缸的密封性下降，缸壓不足，會造成發動機運轉不穩、動力下降，甚至熄火等故障。
分析氣門彎曲的原因，是積碳進入氣門導管造成氣門運動卡滯，活塞上行時將氣門頂彎檢查各人氣缸，可以看到某缸有明顯的拉傷痕跡。拆下活塞檢查，看到活塞環已經嚴重損傷，且活塞環槽記憶體在大量積碳，活塞環背隙被積碳填滿，活塞環直徑加大，猛烈刮擦氣缸壁，造成缸壁拉傷.
什麼是積碳
在發動機工作過程中，燃油和進入燃燒室的機油沒有完全燃燒，產生的膠質在高溫狀態下形成沉積物這就是“積碳”。積碳通常呈黑色，堆積在發動機內的各個位置，包括進排氣門、活塞頂部、火花塞端部、噴油器端部等部件的表面。
積碳表面有許多孔隙，具有吸油的特性，會吸收噴油露噴射出的燃油，導致燃油不能完全燃燒而再變成積碳，如此惡性循環，積碳越來越厚，輕則導致尾氣排放超標、發動機意速抖動、冷起動困難，嚴重時可能使氣門卡滯，導致氣門與活塞發生碰撞造成彎曲。
積碳是如何形成的
發動機內部形成積碳是無法避免的，總會出現不完全燃燒的情況，只要沒有嚴重的積碳即可。導致發動機嚴重積碳的原因很多:燃油品質不佳，或者火花塞點火能量不足，日積月累形成大量積碳;發動機經常處於中低負荷下運轉，例如經常在城市裡走走停停，發動機內部機械部件，例如活塞環或氣門油封老化，導致機油進入燃燒室。
發動機拉缸、頂氣門具體維修過程
話題聚焦回前文提到的故障車，維修人員還進行了以下檢查。將火花塞拆下檢查，發現其端部有較多積碳，可以看出燃燒不完全。
查看安裝在底盤上的燃油源清器，從外觀看已經很久沒有更換過。燃油濾清器超期使用，對燃油的過演能力會大打折扣。燃油不純淨，燃燒品質轉差，使缸內積碳增加。因此，要減少缸內積碳，必須按規定更換燃油濾清器
拆下節氣門連接的進氣管道，可以看到節氣門閥片上有很多積碳。遇到這種情況，除了要清洗節氣門之外，還要檢查發動機空氣濾清器的狀態。這輛車的空濾已經很髒，且看起來比較劣質，雜質較多的空氣進入燃燒室，同樣會影響燃燒品質。
對發動機進行大修，更換活塞環和氣門等部件，清洗節氣門，並更換燃油濾清器和空氣濾清器，試車故障排除，發動機工作恢復正常.
溫馨提示您：
為避免燃燒室內產生大量積碳，首先應選擇燃油品質可靠的加油站，並根據汽車廠商要求定期更換空濾和燃油濾。此外，應避免經常超短距離使用車輛，並密切關注機油消耗量和尾氣的顏色，發現機油消耗過快，則應根據檢查的情況更換氣門油封或活塞環。馬勒提供原廠品質的濾清器產品，以及氣門、活塞、活塞環和氣缸套等發動機部件，如果您想購買到 原產配件聯係我們。
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Case Study:
The car was serviced by the factory because the engine fault warning light was illuminated. After inspection, the engine was also accompanied by difficulties in starting, weak acceleration and rapid stalling. The pressure of a number of cylinders was measured to be lower than the standard value, which was judged to be an internal problem of the engine, so the engine was disassembled.
From the dismantling of the situation, some valve stems have been bent, the valve on the accumulation of a large amount of carbon, the cylinder wall also has signs of strain. The bent valve stem will cause the valve to close tightly, the cylinder seal is reduced, the cylinder pressure is insufficient, which will cause the engine to run unstable, power down, and even stall and other failures.
Analysis of the cause of valve bending, is the accumulation of carbon into the valve guide tube caused by valve movement stuck, the piston up when the valve top bend check each person cylinder, you can see a cylinder has obvious traces of strain. Remove the piston to check, see the piston ring has been seriously damaged, and the piston ring groove memory in a large amount of carbon, the piston ring back gap was filled with carbon, the piston ring diameter increased, violently scraping the cylinder wall, resulting in cylinder wall strain.
What is carbon build-up?
During engine operation, fuel and oil entering the combustion chamber do not burn completely and the resulting gum forms deposits at high temperatures. Carbon deposits are usually black in colour and accumulate on the surfaces of various parts of the engine, including the intake and exhaust valves, the top of the pistons, the ends of the spark plugs and the ends of the fuel injectors.
Carbon deposits have many pores on the surface and have the property of absorbing fuel, which causes the fuel to not burn completely and then become carbon deposits, thus leading to a vicious cycle of thicker and thicker carbon deposits, which may lead to excessive exhaust emissions, engine shuddering and cold start difficulties, or in severe cases, valve sticking, causing the valve and piston to collide and bend.
How carbon builds up
The formation of carbon inside the engine is unavoidable and will always result in incomplete combustion, as long as there is no serious carbon build-up. There are many reasons for serious carbon build-up in engines: poor fuel quality or insufficient ignition power in the spark plugs, which can lead to a large amount of carbon build-up over time; the engine is often run under low to medium load, for example, in the city, and mechanical components inside the engine, such as piston rings or valve seals, deteriorate and cause oil to enter the combustion chamber.
The specific repair process for engine pulling and topping valves
Focusing back on the faulty car mentioned above, the mechanic also carried out the following checks. The spark plug was removed and inspected and found to have a large amount of carbon build-up on its end, which showed incomplete combustion.
Looking at the fuel filter mounted on the chassis, it looked like it had not been replaced for a long time. The fuel filter was out of date and its ability to overhaul the fuel was greatly reduced. The fuel is not pure and the combustion quality deteriorates, resulting in increased carbon build-up in the cylinders. Therefore, to reduce the carbon build-up in the cylinder, the fuel filter must be replaced as required
Looking at the fuel filter mounted on the chassis, it looked like it had not been replaced for a long time. The fuel filter was out of date and its ability to overhaul the fuel was greatly reduced. The fuel is not pure and the combustion quality deteriorates, resulting in increased carbon build-up in the cylinders. Therefore, to reduce the carbon build-up in the cylinder, the fuel filter must be replaced as required
If you remove the intake pipe connected to the throttle valve, you can see that there is a lot of carbon on the throttle valve plate. In this case, in addition to cleaning the throttle valve, you should also check the condition of the engine air filter. The car's air filter is already dirty and looks poor, and the quality of combustion is also affected by impurities entering the combustion chamber.
Overhaul the engine, replace the piston rings and valves and other components, clean the throttle, and replace the fuel filter and air filter, test drive troubleshooting, the engine work back to normal.
A gentle reminder to you:
To avoid large amounts of carbon deposits in the combustion chamber, you should first choose a reliable fuel station and change the air and fuel filters regularly according to the vehicle manufacturer's requirements. In addition, avoid using the vehicle for short distances and keep a close eye on the oil consumption and the colour of the exhaust gas. If you find that the oil is being consumed too quickly, the valve seals or piston rings should be replaced according to the inspection. MAHLE offers original quality filters as well as engine components such as valves, pistons, piston rings and cylinder liners, so please contact us if you would like to purchase genuine parts.
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