LaCrosse 3.0 Throttle Body Replacement Method

Throttle body is an important part of engine electronic control system. After driving a certain mileage, such as about 300 thousand kilometers, the throttle will reach the peak of damage. Common faults include unstable idle speed, idle flameout or excessive idle speed. In addition to the dirty throttle body, sometimes it is also an internal fault of the throttle body. The usual maintenance method is to replace the throttle body as a whole, which will make the maintenance cost very high and cause a certain degree of waste. In the long-term maintenance work, the author found that most of the faults of the throttle body were caused by the damage of the internal idle motor, so the better way to maintain the throttle body is to replace the idle motor.

For a long time, there are not many ways to disassemble and maintain the throttle body, which also leads to the difficulty in purchasing spare motor parts, that is, it is impossible to find a suitable replacement motor, and how to replace the motor also has certain technical difficulties. With the deepening of maintenance technology, idle motors matching the corresponding models have been well selected.

Take the throttle body of Jetta Vanguard 2V engine as an example to explain the replacement method of idle motor, which can be used for reference by other Volkswagen models.

Internal structure of throttle body

The engine control unit controls the throttle body, the idle switch, the idle throttle potentiometer and the throttle potentiometer provide throttle position information to the control unit (J220), and the control unit controls the idle motor to control the throttle opening through gear transmission within the idle range.

(1) The throttle potentiometer (G69) is directly connected to the throttle shaft, and provides throttle position signals in all adjustment ranges for the control unit. In cars equipped with automatic transmission, the control unit also uses this signal to control the automatic transmission. If the control unit does not receive the throttle potentiometer signal, the control unit will use the engine speed and the air flow meter signal to calculate the replacement value.

(2) The idle throttle potentiometer (G88) is connected with the idle motor to inform the control unit of the current position of the throttle and the position of the idle motor within the idle range. When the potentiometer reaches the limit of the adjustment range, the throttle valve continues to open and the potentiometer no longer works. If the signal is interrupted, the throttle body enters the mechanical emergency state by using the emergency spring, and the idle speed increases.

(3) The idle switch (F60) is closed in the whole idle range, and the system recognizes the idle working condition. If the signal is interrupted, the control unit will compare the values of the throttle potentiometer and the idle throttle potentiometer to determine the idle position of the throttle.

(4) The idle motor (V60) operates the throttle valve through gear transmission within the idle speed adjustment range. If the control of the control unit on the V60 disappears or the motor is damaged, the emergency spring will pull the throttle to a specific emergency position.

operation sequence/order

(1) Unscrew the bolt of the rear cover of the throttle body and remove the rear cover, so that the internal structure can be seen clearly. On the surface, it seems that the motor cannot be taken out without destroying the transmission gear between the idle throttle potentiometer and the idle motor. Actually, it's not. We can easily find a breakthrough.

(2) Remove the two bolts that fix the multi-pin socket on the throttle body, and slightly pull out the connecting wire on the socket. At this time, if you look carefully, you will find that there is a 1 hole next to the fixed position of the socket, which is the positioning shaft hole of the transmission gear shaft between the idle motor and the idle throttle potentiometer.

(3) Find suitable iron with high hardness 1, or polish the screwdriver to a corresponding thickness and punch out the gear shaft with the locating shaft hole, so that the transmission gear can be removed. The transmission gear is made of plastic, so be careful not to damage the gear when punching the gear shaft.

(4) Take out the circuit board covered on the idle motor, but a small part of it is blocked by the gear of the idle throttle potentiometer, so it cannot be taken out as a whole. Only part of the plastic of the circuit board can be cut off at the position shown in the figure, and then gently pry the circuit board along the edge gap above the idle motor with a small screwdriver and open it aside.

(5) Remove the locating plate screw on the idling motor, and then take off the locating plate, so as to take out the idling motor. Do some cleaning work, install new motors and modify other parts.

(6) Install the throttle body on the engine, and use the diagnostic instrument for basic setting and trial operation. At this point, the maintenance work is over.

As can be seen from the above example of replacing the idling motor, the replacement process is not difficult. But in the whole operation process, we should be careful and not be too hasty. The components in the throttle body should not be strongly impacted by external force, especially the potentiometer slider and the carbon film resistor on the circuit board should not be scratched. The most important point is that the polarity of idle motor cannot be reversed, otherwise all previous efforts will be in vain.