fuel AUDI A6 1997 C5 / 2.G ATW Engine Motronic Fuel Injection Syst

24-29

Note:

Idle speed cannot be adjusted.
Idle speed is checked during basic setting of
the engine.
During basic setting, the Evaporative Emission
(EVAP) canister purge regulator valve (EVAP
valve -N80-) is closed and the A/C compressor
is switched off

Test sequence

- Check DTC memory Page 01
-16
. There must
not be any DTCs stored, repair malfunctions if
necessary, erase DTC memory, switch engine
off and start again, road test vehicle and check
DTC memory again as a control measure.

- Let engine continue to run at idle.

WARNING!

The electric fan for the radiator must not be
running. Rapid data transfer
HELP
Select function XX

When indicated on display
-
Press buttons -0- and -4- to select "Initiate basic setting" and press -Q-
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button to confirm input.
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24-30

Basic Settin
g
Q
Enter display group number XXX

When indicated on display
- Press buttons -0-, -5- and -6- to select "display group number 056" and
press -Q- button to confirm input.
System in basic setting 56
1
2
3
4

When indicated on display
- Check whether the engine speed in display field 1 (actual engine speed) is
within tolerated range.

Display fields

1 2 3 4
Display group 056: Idle stabilization at operating temperature
Display
xxx /min
xxx /min x.x % X X X X X
Indicated
Engine speed (actual)
Engine speed
(specified) Idle control
Torque
change Operating conditions
Specified
value FWD: 740 to 860 RPM
AWD: 800 to 920 RPM FWD: 800 RPM
AWD: 860 RPM x.x % 0 0 0 0 0
Note
If specified value is not obtained
Page 24
-32

Significance of numbers
Page 24
-32
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24-31

Note:

Engine speed in display field 1 (actual engine
speed) is the current engine speed.
Engine speed in display field 2 (specified
engine speed) is a theoretical engine speed
calculated by the ECM.
At idle, the ECM always attempts to adapt the
engine speed (actual) to the specified engine
speed (specified).
This means that the engine speed (actual) must
always approximately match the engine speed
(specified) at idle.
Display fields 3 and 4 provide information, but
are not relevant for checking idle speed.
If specified value is obtained:

-
Press button.
Rapid data transfer
HELP
Select function XX

Indicated on display (function selection):
If specified value is not obtained:
- Check DTC memory again Page 01
-16
.
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- If DTC memory was erased, readiness code must be re-generated
Page 01
-73
.
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24-32

If idle speed is too high or low and there are
no DTCs in DTC memory, the following tests
(marked with dots) must be performed:

Check for false air in intake air system
Page 24
-68
.

Check throttle valve control module Page 24
-120
.

Evaporative Emission (EVAP) canister purge
regulator valve always open, checking
Page 24
-107
.

Perform adaptation of throttle valve control
module Page 24
-121
.
Significance of 5 digit indication of display group 056 x
x
x
x
x
Display field 4
0 A/C compressor: 0 = A/C compressor off; 1 = A/C compressor on
0 Manual transmission: Indication always 0
Driving mode for automatic transmission: 0 = selector lever in P or N; 1 = selector lever in 2/3/4/D/R
0 Indication always 0
0 Indication always 0
0 Indication always 0
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24-33

System pressure, fuel pressure
regulator and residual pressure,
checking


Note:
Fuel pressure regulator regulates fuel pressure
according to intake manifold pressure. This
ensures that the pressure drop at the fuel
injectors remains the same for each speed and
load range of the engine.

Special tools and equipment

Test requirements:
Repair Manual, Fuel Supply System, Repair Group 20

VAG1318V.A.G 1318 with V.A.G 1318/11 adapter, V.A.G 1318/12 pressure
hose with connectors and V.A.G 1318/13 adapter Fuel Pump (FP) relay OK; checking Page 24
-53
.
Fuel Pump (FP) OK, checking: Fuel filter OK Battery voltage at least 12.7 V Vehicles with automatic transmission Selector lever in P or N.
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24-34

Checking system pressure

- Open fuel filler flap briefly (pressure release).

WARNING!
Fuel system is under pressure! Before opening system, place rags
around the connection point. Then release pressure by carefully
loosening connection. - Remove engine cover (arrows).

- Open threaded connection (arrow) and catch exiting fuel using a rag.
- Connect VAG1318 pressure gauge in supply line using adapters
1318/11, 1318/12 and 1318/13.
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24-35


- Open shut-off valve of pressure gauge. The lever points in the direction
of flow.
- Start engine and let run at idle.
- Measure fuel pressure.

Specification: about 3.5 bar positive pressure

- Disconnect vacuum hose at fuel pressure regulator.

Fuel pressure must rise to about 4.0 bar positive pressure.
- Switch ignition off.
- Check for proper seal and residual pressure by observing pressure
drop on pressure gauge.
After 10 minutes, there must be at least 2.5 bar positive pressure
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24-36
If residual pressure sinks below 2.5 bar positive
pressure:

- Start engine and let run at idle.

If pressure does not drop now:
If pressure drops again:
If pressure does not drop now: - Wait until pressure has dropped, and then switch off ignition.
Simultaneously close shut-off valve of VAG1318 pressure gauge (lever
perpendicular to direction of flow -arrow-).
- Observe pressure drop on pressure gauge.
- Test check-valve on Fuel Pump (FP).
- Open shut-off valve of pressure gauge. The lever points in the direction
of flow.
- Start engine and let run at idle.
- Wait until pressure has dropped, and then switch off ignition.
Simultaneously clamp return line (with blue marking) completely
closed.
- Replace fuel pressure regulator
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