A 2009 Chevrolet Jingcheng car with a mileage of about 130 thousand km, equipped with L34 engine and automatic transmission. Users reflect: the car speeds up when driving. After the car: the maintenance staff test, found that the speed of the car reached 80 km/h, engine speed has exceeded 3000 r/min, indicating that the engine at this time the load rate is too high. Detect engine control unit and find fault code P0171---- mixed gas dilute and P0300---- multi cylinder fire. When the vehicle accelerates, it is observed that the intake air pressure is only 32 kPa. Such a value is only when the engine is idle. When the vehicle accelerates, the output torque of the engine is greatly increased and the intake volume will increase significantly, and the air pressure data obtained by the engine control unit at this time is obviously not normal. Troubleshooting: replace intake pressure sensor, troubleshooting trial run.