Engine troubleshooting

Excessive fuel consumption
Engine fuel consumption malfunction:
Excessive engine fuel consumption refers to fuel consumption exceeding the specified standard value per 100 kilometers. Excessive fuel consumption will lead to poor engine economy. Many factors affect engine fuel consumption, including those related to engine technology and chassis technology.
1. Malfunction phenomenon: Excessive engine fuel consumption.
2. Common causes of malfunctions
1) Coolant temperature sensor malfunction.
2) Air flow meter or intake pressure sensor malfunction.
3) Throttle position sensor malfunction.
4) Excessive fuel pressure.
5) Cold start injector leakage or cold start control malfunction.
6) Injector leakage.
7) Oxygen sensor malfunction.
8) Ignition system malfunction.
9) Engine mechanical component malfunction (low cylinder pressure, etc.).
10) Incorrect valve timing.
11) ECU and connector malfunction.
3. Fault diagnosis and troubleshooting
1) The resistance value of the coolant temperature sensor at different temperatures should meet the standard. Excessive resistance value will cause the computer to mistakenly believe that the engine is at a low temperature, leading to increased cold car boost control and fuel consumption. You can also use a computer decoder to detect the coolant temperature value displayed by the coolant temperature sensor detector to the computer and compare it with the actual engine coolant temperature. If there is a discrepancy, it indicates that the coolant temperature sensor is malfunctioning and should be replaced.
2) Detect the air flow meter or intake pressure sensor; its value should meet the standard. Errors in the air flow meter or intake pressure sensor will directly affect the fuel injection amount. If the detection result is abnormal, the air flow meter or intake pressure sensor should be replaced.
3) Check the throttle position sensor. When the throttle is in the medium-small opening position, the full-load switch should be disconnected. If the full-load switch is always closed or closes too early, it will cause the computer to continuously or prematurely perform full-load boost, thereby increasing fuel consumption.
4) Measure the fuel pressure. At idle speed, the fuel pressure should be around 250 kPa. As the throttle opens, the fuel pressure should gradually increase. The fuel pressure when the throttle is fully open is approximately 300 kPa. If the fuel pressure can change with the throttle opening, but the pressure is still very high, it indicates that the fuel pressure regulator is malfunctioning and should be replaced. If the fuel pressure does not change with the throttle opening and remains at around 300 kPa, it indicates that the vacuum hose of the fuel pressure regulator is broken or detached, or the fuel pressure regulating solenoid valve is malfunctioning, and the vacuum in the intake pipe cannot act on the vacuum diaphragm chamber of the fuel pressure regulator, resulting in excessive fuel pressure. For this, the hose or solenoid valve should be replaced. If the fuel pressure is too high, exceeding 400 kPa, it indicates that the return oil pipe is blocked or the fuel pressure regulator is malfunctioning. The return oil pipe should be checked or the fuel pressure regulator should be replaced.
5) Check the ignition high voltage, energy, and ignition timing.
6) Check whether the cold start fuel injection control is normal. Connect a voltmeter or test lamp to the wire harness connector of the cold start injector to check whether the working time of the cold start injector when the engine starts meets the standard value. If the working time is too long or continues to work after starting, it indicates that the control of the cold start injector is abnormal. The cold start temperature switch and control circuit should be checked.
7) Remove the injector and check each injector for leaks. If there are any abnormalities, the injector should be cleaned or replaced.
8) Check the engine for mechanical malfunctions (cylinder pressure, valve sticking or leakage, camshaft wear, valve timing, valve clearance, valve sealing, etc.), check whether the exhaust system is blocked, and check the working condition of the cooling system thermostat.