The old Mercedes-Benz 300 washes the throttle and idles at a higher speed.

Generally speaking, there are several reasons for high idle speed.

First, the idle valve is damaged. It is recommended to check or replace the idle valve.

Second, the throttle position sensor signal is incorrect or no signal.

Third, the air intake pipe leaks, especially for cars with intake pressure sensors.

Fourthly, there is something wrong with the electronic control system, so it is suggested to read the data stream with a decoder.

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