Check the intake manifold sequence valve with tester A in «Gefuehrte Fehlersuche/Guided Fault Finding».
If the intake manifold changeover valve is OK, perform the following checks
Checking procedure
Remove the vacuum drive cover.
Start the engine and let it run at idle speed. Vacuum drive retracted.
The assistant should sharply press the accelerator pedal. Watch the intake manifold vacuum switch actuator, it should switch.
If the switch does not work. as described above, check the tightness of the vacuum system, including the vacuum reservoir on the intake manifold.
Check the ease of movement of the shift mechanism. To do this, pull the drive rod by hand.
Check that the vacuum lines are connected correctly.
Check vacuum hoses for porosity.
Disconnect the vacuum hose to the intake manifold vacuum changeover actuator from the intake manifold changeover valve 1.
Pic. 2.236. Connecting a Hand Vacuum Pump to the Intake Manifold Vacuum Switch Actuator
Connect a hand vacuum pump to the intake manifold vacuum shift actuator (pic. 2.236).
Press the hand vacuum pump several times. The vacuum drive rod must move.
If the intake manifold changeover actuator does not move
Replace the vacuum actuator.
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