Checking intake air system for leaks (unmetered air) — AUDI

ALZ
Special tools and workshop equipment and additional materials required:

VAS 5051 with VAS 5051/1

or

V.A.G 1551 and V.A.G 1551/3 A
Engine leak detector spray G 001 800 A1

Notes:

The vacuum in the intake system will cause the leak detector spray to be drawn in with the outside air. The leak detector spray reduces the ignitability of the mixture. This leads to a drop in engine speed and to a significant increase of the CO content.
The safety precautions listed on the container must be adhered to.

Test sequence

Connect vehicle diagnostic, testing and information system VAS 5051 (or fault reader V.A.G 1551) and select engine electronics control unit by entering address word "01" ( => Page
01-12
.)
When doing this the engine must be idling.

Rapid data transfer
HELP
Select function XX
Indicated on display:

Enter "08" to select the function "Read measured value block" and confirm entry with Q key.

Read measured value block
Q
Enter display group number XXX
Indicated on display:

Enter "001" to select Display Group 001 and confirm entry with Q key.

Read measured value block
1
⇒
1
2
3
4
Indicated on display:
(1...4 = Display zones)

Note engine speed in display zone 1.
Systematically spray parts of the intake system with engine leak detector spray.

If the engine speed does not change:

Press the ⇒key.

Rapid data transfer
HELP
Select function XX
Indicated on display (function selection):

If the engine speed drops:

Press the ⇒key.
Enter "06" to select the function "End output" and confirm entry with Q key.
Switch off ignition.
Check sprayed areas of intake system for leaks and rectify if necessary.

Testing integral vacuum reservoir in intake manifold for leaks (supplies vacuum for intake manifold change-over function, etc.)

Run engine at idling speed for several minutes. Make sure that the hoses and hose connectors for -N156 (intake manifold change-over valve) are in good condition (all parts properly fitted and airtight).
Perform test of intake manifold change-over function. This test also serves to check for leaks in the integral vacuum reservoir => Page
24-142