Variable Induction System: Testing and Inspection

CHECKING INTAKE MANIFOLD CHANGE-OVER FUNCTION
Carry out this test only when there are performance complaints.
The change-over of the intake manifold from long to short intake path occurs at approx. 4000 RPM.

CHECKING FUNCTION
- Increase engine speed to over 4000 RPM.
^ Vacuum unit,located on left rear of compound intake manifold, for intake manifold change-overvalve must operate

If the change-over does not occur, perform the following tests:
- Use On-Board Diagnostics (OBD) output diagnostic test mode (DTM) to activate fuel pump relay -J17-. Testing and Inspection
- Check operation of intake manifold change-over valve during On-Board Diagnostics (OBD) Output Diagnostic Test Mode (DTM).

If necessary check valve and actuation:
- Check to make sure vacuum reservoir and lines are free of leaks and restrictions.
- Check vacuum hoses for correct connection.
- Check mechanical action of intake manifold change-over valve for ease of movement (operate rods by hand).
- Switch ignition OFF.
- Disconnect vacuum hoses from intake manifold change-over valve vacuum unit.
- Connect hand vacuum pump to vacuum unit.
- Operate hand pump to apply vacuum, and observe change-over process.
- Check vacuum unit for leaks.
^ The vacuum unit must not return to its original position as long as vacuum is maintained.
- If necessary, replace vacuum unit.

If no malfunctions were determined in the previous tests:
- Disconnect harness connector from valve and connect valve terminals to battery positive voltage (B+) and Ground (-) using adapter cables from VW 1594 connector test kit (if necessary, remove valve).
^ Valve must be clear (detach vacuum lines and blow through)
- If necessary, replace intake manifold change-over valve.

CHECKING VACUUM SYSTEM
- Let engine idle 2-3 minutes (to fill vacuum reservoir).
- Switch ignition OFF.
- Disconnect harness connector (2-pin) from intake manifold change-over valve.
- Connect one terminal of valve to Ground (GND) using harness and clip from VW 1594 connector test kit.
- Connect second terminal of valve to battery positive voltage (B+) using remote control VAG 1348/3A, adapter harness VAG 1348/32 and adapter cable.
- Operate remote control VAG 1348/3A approx. 2-3 minutes.
^ Vacuum unit must remain activated