Instantaneous surge occurs when the engine speed reaches 3000 rpm.

Phenomenon: Customers report that cars often surge, and every time there is surge, the throttle (accelerator pedal) is almost in the same position, and at the same time, the fuel consumption increases and the power decreases.

Analysis:

1. The throttle position sensor is faulty.

2. The crankshaft position sensor is faulty and the signal is unstable.

3, ignition system failure, resulting in a lack of fire in a coincidence.

4. Accidental failure of air flowmeter

Diagnosis:

1. Call the fault code, indicating that the mixture ratio is poor. It can be inferred that the fault is inevitably related to the throttle opening. Using oscilloscope to detect the throttle position sensor, it shows that its waveform shows a gentle downward trend with the increase of throttle opening, and its orientation is smooth and burr-free, indicating that the throttle position sensor is normal.

2. Because of another fault phenomenon, the fuel consumption increases and the power decreases. The air flow meter and oxygen sensor were tested, and the air mass flow rate was 4.8g/s at idle speed, and the signal voltage of oxygen sensor showed about 0.8V. To verify the quality of O2S, the engine started to idle at high speed after pulling out a vacuum tube on the intake manifold, and the signal of O2S decreased from 0.8V to 0.2V, indicating that it was normal. However, during the idling operation, the air flow kept swinging at a small amplitude of 4.8g/s. After unplugging the plug of the air flow meter, the test was started again, and the fault disappeared. Troubleshooting after replacing the air flow meter.

Summary:

When a sensor is suspected to be faulty, the method of unplugging the sensor plug (the crankshaft position sensor can't be unplugged, otherwise the vehicle can't start) can be used for testing. When a plug is unplugged, the control of ECU will enter the standby program and be replaced by stored or other signal values. If the fault disappears after unplugging, it means that the fault is related to the sensor.