7/31/2019 Idle Control Valve Controls Idle Speed Under Load Such As

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Idle Control Valve controls idle speed under load such as:

- cold start

- in gear

- when heavy loads are on, eg. air conditioning, extra heavy electrical loads

- depending of the vehicle speed

The overvoltage protection relay receives the loads present in the electrical system by means of

overvoltage response in the associated electrical circuit or electrical control by the fuel pump

relay and closes the power circuit from the power feed hot at all times (usually pin 1 on the OVP

relay and the pin 2 on the ICV, if it has 2 pins, if it has 3 pins it also receives activation from the

TPS or the fuel cut-off microswitch or the automatic transmission upshift delay relay) with the

idle speed control on the computer (which acts like a controlled resistance ground, controlling in

function of all imput factor it receives, that's why when you grounded the computer idle speed

control its role was replaced and it tried to adjust the idle to a higher value, probably sensing a

load condition and adjusting the other engine controls such as the ignition mole or the fuel

distributor's electrohydraulic actuator which increases the lower chamber fuel pressure and

increasing the idle). As the valve closes after cold start operation or after a heavy load isdisconnected, the air excess needed for the engine to support the load and maintain its idle speed,

is cut and the engine returns to its normal idle. A faulty Idle Control Valve could have the

following symptoms: worn solenoid valve inside, dirty stuck plunger inside, excessive resistance

in its internal circuit that prevents the solenoid to close for the same applied voltage.

In conclusion, the Idle Control Valve receives control voltage (to keep it open to supply

additional air supply to the engine) only when it's needed (cold start, temporized 10 or 28

seconds, under a certain vehicle speed, when the AC is on, in gear, or any other excessive load).

Think of it as the classic carburetor choke, only that in this case is electronically controlled and

participtes in the engine management.

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Mercedes B klasse 2006 - Hergestellt in Deutschland