4-Cylinder Engine Troubleshooting Guide

The previous article introduced the common engine troubleshooting methods, this article will take 4-cylinder engine as an example, continue to introduce you.

1. Rattling diagnosis: locating the source of the fault according to the sound

The mechanical rattling of 4-cylinder engine often directly reflects the state of key components. When there is a metallic knocking sound, it is necessary to prioritize the investigation of whether the signal of the detonation sensor is abnormal, or try to fill with high-grade gasoline to verify whether the detonation is triggered by insufficient octane value of the fuel. If it is accompanied by a drop in power, you need to further test the ignition advance angle parameters.

Sharp whistling mostly originates from the accessory belt system. When checking the surface of the belt can be sprayed with water spray, if the noise disappears, it indicates that the belt is aging and slipping, and you need to check the lubrication status of the tensioner wheel bearings at the same time.

Low knocking sound need to stop immediately for maintenance. This kind of sound is usually related to the crankshaft main bearing or connecting rod bearing wear, can be detected through the oil pressure gauge main oil pressure.

2. Exhaust gas color analysis

Tail gas color is an important window to determine the quality of engine combustion. Black smoke indicates that the mixture is too thick, should focus on checking the accuracy of the air flow meter signal and injector atomization effect.

Blue smoke is a typical characteristic of oil burning. By testing the negative pressure value of the crankcase ventilation system, you can judge the piston ring sealing performance. If the negative pressure value is lower than -15kPa, it is necessary to conduct a wet cylinder pressure test: inject a small amount of oil into the combustion chamber and then measure the cylinder pressure again, if the pressure is significantly increased, it is confirmed that the piston ring is worn out; if the pressure change is small, it is necessary to check the sealing of the valve oil seal.

White smoke is a normal phenomenon in winter, but continuous white smoke should be alerted to coolant leakage. The HC value can be measured by exhaust gas analyzer, if the value is abnormally high, it is necessary to carry out cylinder pressure test and cooling system pressure test, focusing on checking the sealing of the cylinder gasket and the cracks in the cylinder waterway.

3. Grasp the timing of maintenance

When there is a red warning such as flashing engine fault light and oil pressure alarm, you should immediately pull over and contact rescue. For yellow warnings that can continue driving, such as occasional shaking or slight noise, diagnosis needs to be completed within 24 hours. Using a diagnostic instrument to read the freeze frame data and compare the speed and load parameters at the time of the fault, the fault trigger conditions can be pinpointed.

The failure characteristics of 4-cylinder engines are becoming increasingly complex. When encountering uncertain conditions, timely capture of video and audio data at the time of failure, combined with real-time data streaming from the on-board data logger, can provide a key diagnostic basis for the service technician. Remember, 80% of engine overhauls originate from the neglect of initial rattling, and the establishment of a scientific failure response mechanism can effectively extend product life.