engine AUDI A4 1999 B5 / 1.G AWM Engine Charge Pressure Leak Test Workshop Manual

21-17

WARNING!

Use only approved air fittings to adapt shop
air supply line to VAG 1687 tester.

Special tool VAG 1687/1 pressure adapter,
installing (1.8L Turbo)

- Separate intake hose from Mass Air Flow (MAF)
sensor assembly.

Special tool VAG 1687/1 pressure adapter, installing (2.7L BiTurbo)
Repair Manual, Maintenance; Air cleaner housing, cleaning; Air cleaner element, replacing
- Insert VAG 1687/1 pressure adapter in intake hose -black arrow- using
existing clamp (as shown).
- Remove crankcase ventilation tube from intake hose at -white arrow-.
- Remove upper air cleaner housing and hoses to intake manifold as
necessary

- Insert VAG 1687/1 pressure adapter in intake hose -white arrow- using
existing clamp (as shown).
- Disconnect engine crankcase ventilation hose from intake manifold -
black arrow-.
-
Plug intake manifold fitting (for crankcase ventilation hose) with
appropriate hose and metal plug using clamps supplied with VAG
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21-19

Special tool LKI9210 (Evaporative system
leak detector), preliminary set-up

- Connect smoke generator leads to vehicle
battery.

With system filled with smoke:
Special tool VAG 1687, connecting to pressure adapter VAG 1687/1
(1.8L Turbo)
For illustrations purposes VAG is shown lying in the engine compartment.
In practice the tool should be hung from the hood. - Turn valve to test -black arrow-.
- Press smoke generator button to fill system with smoke (see
instructions printed on tester).
- Remove smoke generator hose and connect VAG1687 quickly to
prevent smoke from leaking out Page 21
-19
.
- Connect VAG 1687 quickly to prevent smoke from leaking out.

VAG 1687 is shown connected to VAG 1687/1 -black arrow-
Shop air supply will be connected to VAG 1687 -at white arrow-
- Perform pressure test Page 21
-21
.
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21-20

Special tool VAG 1687, connecting to
pressure adapter VAG 1687/1 (2.7L BiTurbo)
For illustrations purposes VAG is shown lying in
the engine compartment. In practice the tool
should be hung from the hood.

- Connect VAG 1687 quickly to prevent smoke
from leaking out.

VAG 1687 is shown connected to VAG 1687/1 -black arrow-
Shop air supply will be connected to VAG 1687 -at white arrow-
- Perform pressure test Page 21
-21
.
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21-21

Performing pressure test:

- With outlet hose -1- of VAG 1687 connected to air pressure adapter:
- Attach shop air supply line to previously installed male fitting Page
21
-16
.

CAUTION! - Open valve -3- between regulator valve and gauge.
- Adjust test pressure up to 0.5 bar ( CAUTION below) by turning
regulator valve -2-.
DO NOT pressurize the system above 0.5 bar!Doing so may force oil into the intake system which can damage
the engine.
- Slowly open outlet valve -4- (after gauge) to test hose connections.
- Observe pressure gauge for a drop in pressure.
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21-24

Mechanical air recirculation valve,
checking


Note:

The mechanical air recirculation valve is
upstream of the exhaust turbocharger. It is
opened via vacuum by the recirculating valve
for turbocharger -N249- under conditions of
overrun, idling and partial load. This reduces
the charge pressure upstream of the throttle
valve. A high turbocharger speed is thus
maintained.
Check the air recirculation valve if the engine is
not producing full power, or jerking when the
throttle is opened and closed.

Special tools and equipment

Hand vacuum pump VAG 1390
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21-27

Test requirements:

Vehicle diagnostic, testing and information
system VAS 5051 or VAG 1551 Scan Tool
connected.

Test sequence

Note:
The recirculating valve for turbocharger -N249-
and the wiring connections are monitored by the
engine control module.

- Read Diagnostic Trouble Code (DTC) memory
of engine control module.
If a DTC relating to the recirculating valve for
turbocharger -N249- is displayed:

Note:
The illustration shows bottom view of removed intake line. - Remove hoses of recirculating valve for turbocharger -N249- (-1-). The
electrical connector remains plugged in.
Location: below intake line
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21-30

Checking power supply

Note:
The power supply for the recirculating valve is via
the fuel pump relay.

Test requirements:

Fuse for recirculating valve OK.

Electrical Wiring Diagrams, Troubleshooting &
Component Locations binder

Fuel pump relay OK.

Repair Manual, 1.8 Liter 4
-Cyl. 5V Turbo Fuel
Injection & Ignition, Engine Code(s): AWM, Repair Group 24


- Disconnect wiring connector from valve.

- Connect voltage tester VAG 1527 B as follows:Connector
Measure to
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contact
1 Engine Ground
- Operate starter briefly.
The LED must light up.
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21-32
If the LED lamp does not flash or if it lights up
continuously:

- Connect VAG 1598/31 test box to wiring
harness leading to engine control module;
engine control module should not be connected:

Repair Manual, 1.8 Liter 4
-Cyl. 5V Turbo Fuel
Injection & Ignition, Engine Code(s): AWM, Repair Group 24


If the wiring is OK: - Check for open circuit and short to positive or Ground in following
wiring connection: Connector
Contact
Test box VAG 1598/31
2 105
- Repair any open/short circuit as necessary.
- Replace engine control module.
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21-34

Test requirements:

Vehicle diagnostic, testing and information
system VAS 5051 or VAG 1551 Scan Tool
connected.

Test sequence

Note:
The Wastegate Bypass Regulator valve -N75-
and the wiring connections are monitored by the
engine control module.

- Read Diagnostic Trouble Code (DTC) memory
of engine control module.
If a DTC relating to the Wastegate Bypass
Regulator valve -N75 is displayed:

- Disconnect hoses from valve but leave electrical
connector attached.

- Connect auxiliary hose to valve connector marked with an arrow.
- Initiate output Diagnostic Test Mode (DTM) and actuate Wastegate
Bypass Regulator valve -N75-.
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