There are many reasons for high fuel consumption of engine. Generally speaking, when the power of the engine is insufficient or black smoke is emitted, the fuel consumption of most engines is too high in this case. This problem should not be ignored when troubleshooting. As for how to eliminate the problem of high fuel consumption, the following steps can be followed.
1. External inspection. Carefully ask the driver about the phenomenon of the fault, the time and situation of the fault, and roughly judge whether the fault is caused by the mechanical system or the electronic control system. At the same time, the fault code can also be called by the fault diagnosis instrument. If there is a fault code, remove it according to the content indicated by the fault code; If there is no fault code, basic inspection can be carried out first. Before the inspection, the first external inspection, including two aspects.
1) Check whether the sensor connector falls off. Open the hood, check whether the connector of each sensor is loose or broken one by one, gently pull it by hand, and plug in the sensor. The sensor with more dust should be cleaned to avoid affecting the signal transmission effect.
2) Check whether the pipe joint is damaged or not. Check whether the air inlet system pipe is broken and leaking, whether the joint is loose, whether the oil inlet pipe and joint are leaking, deal with the place where oil leakage and air leakage are found, and clean and replace the air filter element in time.
2. Basic inspection
1) Check the fuel system pressure. If the pressure is too high, check whether the fuel pressure regulator is normal, whether the filter screen is blocked, and whether the gasoline filter is blocked.
2) Check the spark plug and high voltage wire. Check whether the spark plug electrode ablation is serious, if it is serious, it should be replaced in time; At the same time, check whether the high-voltage line has leakage phenomenon, if so, it should be replaced in time. After the spark plug is ablated and the insulation of high voltage line is broken down, the ignition energy is easy to be insufficient, which leads to the problems of poor combustion quality, insufficient power and high fuel consumption.
3) Check the fuel injector. When the fuel injector is damaged or blocked, there will be idle cylinder missing, weak acceleration, exhaust pipe blasting, shrugging phenomenon or feeling of insufficient fuel supply when accelerating; The fuel consumption is too high.
For the inspection of the fuel injector, pull off the plug of the fuel injector connecting to the computer, and measure the voltage value of each pin with a multimeter. This value should be the voltage value of the battery, otherwise it will be regarded as the open circuit of the electromagnetic coil; Measure the resistance value between two pins of each injector. If it is 0, it means short circuit. The standard value of resistance should be 13-18 Ω( Jetta engine).
3. Electric control system inspection
(1) Check the oxygen sensor. There are two main types of oxygen sensor faults; The circuit is faulty and the oxygen sensor is not working well.
Line fault. It can be divided into external circuit fault and internal circuit fault. When this kind of fault is detected by computer, there is a fault code, which can check whether the external circuit has grounding and open circuit. For internal and external circuit fault, the oxygen sensor can be replaced directly.
The oxygen sensor is not working well. There is no fault code when the computer detects this kind of fault. When using data stream diagnosis, the value of shot value is unstable and exceeds the standard value ± 25% or change slowly, generally the oxygen sensor is faulty and needs to be replaced.
(2) Check the air flow meter. There are two main forms of air flow meter fault: circuit fault and no fault code in computer detection.
The circuit fault is divided into external circuit and internal circuit. When the computer detects the fault code, check whether the connection between the plug and the computer of the external circuit is open circuit and grounded. If it is normal, the air flow meter is damaged and should be replaced.
It is common that there is no fault code when the computer detects. At this time, due to dirty and other reasons, the value reflected by the air flowmeter has a certain deviation, resulting in high fuel consumption. When checking with data flow, focus on checking whether there is deviation between the injection time and the normal time (for example, Jetta's normal injection time is 1.6 ~ 1.8ms), whether the injection time is too long, then check whether the intake volume is too large (the normal intake volume is 3.0 ~ 4.0g / S), and whether the engine runs stably and shakes at idle speed. In case of these phenomena, the air flow meter should be replaced in time.
(3) Check the intake air temperature sensor and coolant temperature sensor. When the computer detects the fault code, the multimeter can be used to measure the resistance to check whether the two sensors are damaged