one. The cause of the failure
The internal failure of the TFI4 air flow sensor leads to an error in the intake model, which affects the opening of the EGR valve and the intake throttle valve, resulting in insufficient engine air intake, and abnormal combustion in the cylinder, which not only causes loss of engine power, but also causes The actual carbon load in the DPF increases sharply, which affects the regeneration of the DPF.
two. Structure and working principle
1. The installation position of the TFI4 differential pressure air flow sensor is behind the intercooler and the air intake pipe before the electronic control air intake throttle.
2. TFI4 differential pressure air flow sensor structure
3. Working principle of TFI4 differential pressure air flow sensor
It measures the mass flow of fresh air and integrates a differential pressure sensor, a temperature sensor, an intake air pressure sensor, and a microprocessor.
When the intake air passes through the roar port A2, the air pressure decreases, that is, A2<A1. The pressure difference between A1 and A2 is measured by the venturi tube and converted into the gas flow rate. The gas density is measured and calculated by the temperature sensor and the pressure sensor. It can calculate the mass flow kg/h, and complete the closed-loop control of the air-fuel ratio through the air mass flow.
4. Characteristics of TFI4 differential pressure air flow sensor
◆Optimized the temperature compensation test of -50℃～250℃;
◆CAN communication, high measurement accuracy;
◆Special design to ensure very low drift based on differential pressure sensor;
◆The direction of the venturi inlet pipeline determines the sensor measurement value, so the value of the air intake model of the TFI4 sensor is different for different models, so it needs to be checked;
Venturi tubes for different engines are not allowed to be replaced at will!
5. TFI4 differential pressure air flow sensor line connection
Three. TFI4 differential pressure air flow sensor use precautions
① When the intake air flow sensor is inserted into the installation hole, do not damage the probe.
②Do not use a striking tool (hammer) to forcibly install the sensor.
③Pay attention to the alignment of the two O-rings during installation to prevent falling off.
④Do not apply grease, lubricating oil, etc. to the sealing ring.
⑤Before installing the sensor connector, make sure that the sensor pins and connectors are clean.
⑥The sensor is completely pressed on the mounting plate of the main body of the venturi.
⑦Clear the engine fault code and confirm that the above faults are no longer reported.