A8 Quattro Sedan V8-4.2L (BFM) (2005)
Intake Manifold: Testing and Inspection
Intake Manifold Change-Over, Checking Function
Intake Manifold Change-Over, Checking Function
‹› The following test should only be performed if there is a performance deficiency.
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Increase engine speed to noticeably above 5400 RPM.
Specified value: Vacuum diaphragm for the intake manifold changeover must activate.
If vacuum diaphragm does not activate:
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Check vacuum lines for proper connection, sealing and continuity, overview.
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Check whether the change-over mechanism moves easily. (Operate change-over linkage by hand as a test).
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Check-valve (black/white) leaky, clogged or incorrectly installed.
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Intake Manifold Change-Over Valve faulty (does not switch through or clogged).
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Check Intake Manifold Change-Over Valve (N156) => [ Intake Manifold Change-Over Valve, Checking ].
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Check vacuum system for proper seal => [ Vacuum System, Checking for Leaks ].
Overview: Intake manifold change-over
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Intake Manifold Change-Over Valve (N156)