Idle/Throttle Speed Control Unit: Testing and Inspection

Testing electronic idle speed control

Preceding work:
Testing, adjusting engine. Engine Testing, Adjustment

Test and Adjustment Data:

Special Tools:

Commercially Available Testers:

a) idle speed air valve with 3-pin connection

Key To Symbols:

Note
^ If the specified value of a test step, e.g. step 4.0, is in order, it is not necessary to perform test step 4.1. Different component designations are possible depending on the wiring diagram or vehicles with optional equipment. These designations are given in parentheses. This has no effect on the test (connections, specified value).
^ Idle speed control is independent of the air flow sensor potentiometer.
^ Engine speed increases when the coupling is disconnected from the decel fuel shutoff microswitch.
^ Test TD signal if readout on tester fluctuates and engine surges.

Test conditions:
^ Intake system without leaks.
^ Slide in idle speed air valve operates freely.
^ Engine oil temperature approx. 80 °C.
^ Coolant temperature sensor, decel fuel shutoff microswitch and idle speed detection throttle valve switch (RUF/KAT) in order.



^ Engine 102.983 Std.
Connect engine tester test cable (4) to test connection of idle air control valve X11/9.




The idle air control valve test connection X11/9 is located on the right in the component compartment.

Test Steps 1.0 - 1.3:

Test Steps 2.0 - 5.1:

b) Idle air control valve with 2-pin connection

Key To Symbols:

Note
^ If the specified value of a test step, e.g. step 4.0, is in order, it is not necessary to perform test step 4.1. Different component designations are possible depending on wiring diagram and vehicles with optional equipment. These designations are given in parentheses. This has no effect on the test (connections, specified value).
^ Engine speed increases when the coupling is disconnected from the deceleration shutoff microswitch.
^ As of 09/88 and model year 1989: idle speed control with road speed signal. The idle speed is deactivated from approx. 1.4 km/h.
If the complaint "jerking when car moving with throttle valve closed" is indicated, test the road speed signal.
^ As of 09/89 and model year 1990: idle speed control with heating speed. This is activated for not more than 28 seconds after each start (conditions: closed throttle position contact closed and selector lever in position "P" or "N").

Test conditions
^ Engine coolant temperature sensor, decel fuel shutoff microswitch and idle speed detection throttle valve switch (RUF/KAT) in order.
^ Intake system not leaking.
^ Engine oil temperature approx. 80°C.

Test Steps 1.0 - 1.4:

Test Steps 2.0 - 6.0: