Mercedes-Benz W201 throttle linkage, return springs and idle switch
W201 throttle does not return properly or idle is high: is a return spring broken?
Throttle return relies on two springs, one of which is on the throttle body under the injection unit. A broken spring leaves the pedal movement loose and the revs hanging high. The lower spring is seen by removing the fuel distributor. A stiff linkage can also be lubricated.
What does the throttle microswitch do in a W201?
The microswitch tells the control unit that the throttle is closed, that is, the engine is at idle. A spring presses the lever against the switch. If the spring is missing or the switch is faulty, idle is not recognised correctly, and the revs may rise or the idle may surge. The switch can be measured with a multimeter.
How is the W201 throttle position sensor measured?
Unplug the connector and measure the resistance with a multimeter. With the throttle closed, the middle terminal must be connected to one outer terminal, and with the throttle fully open to the opposite one. Dirty or worn contacts can make the idle swing, and cleaning can help.