The fuel tank cover of BMW 5 Series is not tight, and the engine fault light is on.

The following reasons are for reference only, 1, sensor failure,; 2. The gasoline quality is not up to standard; 3. Air leakage in the intake pipe causes the mixture to be too thin; 4. The fuel pressure is low, and the fuel injector and fuel filter are blocked; 5. Abnormal signals of pressure sensor and throttle position sensor; 6. Abnormal sensor signal leads to inaccurate ignition timing and delayed ignition; 7. Poor spark plugs, igniters or high-voltage lines lead to weak high-voltage sparks; 8. The throttle valve is dirty; 9. The exhaust gas recirculation system is not working properly; 10, the exhaust pipe is blocked; 1 1, low cylinder pressure; 12, turbocharging system failure 13, clutch three-piece failure 14 air filter blockage, piston ring fracture or seizure, poor valve seal, too late ignition time, mechanical failure of carburetor, air leakage in intake pipe, bad or non-working individual cylinders, etc. However, some faults of insufficient engine power can be solved by use. For example, the cylinder is generally worn, and the carburetor oil circuit is not circulating smoothly. When users report that the engine power is insufficient and the engine oil is burned, they should first judge the reason for the lack of power. The working condition of carburetor can be judged according to whether the engine oil consumption is too high after eliminating the reasons such as air filter blockage, carburetor throttle valve not fully opened, poor ignition timing, damaged intake pipe gasket, and individual cylinders not working or not working well. If the fuel consumption is too high and the exhaust gas is thick, it is likely that mechanical faults such as metering hole falling off will occur, which must be repaired. Finally, let's judge the wear of the engine cylinder. Engine wear directly affects the tightness of the cylinder; Therefore, checking the tightness of the cylinder can reflect the wear degree of the cylinder to a great extent, and the most convenient way to check the tightness of the cylinder is to check the compression pressure of the cylinder with a cylinder pressure gauge.