What is the reason for the high idle speed after cleaning the throttle?

Due to the influence of dirt on the throttle body, sludge keeps accumulating on the edge of the throttle. Under the idle condition, the idle intake of the straight-through idle control system is obtained by the motor pushing the throttle opening, and the throttle opening is very small at idle. Due to the sludge jam at the edge of the throttle valve, the intake air is insufficient, which makes the engine speed decrease. When it deviates from the standard speed, the electronic control unit outputs a larger signal, instructing the motor to continue to increase the opening to maintain the target speed. This new opening data (motor position sensor signal) replaces the old opening data again, and at the same time, it is stored in the memory of the electronic control unit as the new optimal data for controlling the motor. With the passage of time, sludge accumulates, and the motor on signal is constantly updated and stored. At this time, the opening is just suitable for the air inlet blocked by sludge, thus ensuring the current idle speed.

Once the sludge is removed, the ECU still controls the throttle opening according to the memory, and at this time, the intake air volume will inevitably increase corresponding to the opening, resulting in an increase in idle speed. It takes time and a process of repeated learning and memory to return to the optimal idle speed.

If you use the diagnostic instrument for setting, the optimal idle speed data will immediately replace the data before cleaning, so that the engine speed will immediately return to the optimal target speed.

If there is no diagnostic instrument setting, you need to repeat the relearning process 1 time, constantly refresh the old data and store new data, and you can also return to the optimal idle speed. The duration of this process depends on different vehicle control systems.

Some manufacturers' products, such as Toyota, can clear the learning value as long as ECU and electronic throttle are powered off for 30s; Some manufacturers' products, such as Lu Zun, need the original diagnostic instrument to refresh the control program (also called programming).