AUDI A4 1998 B5 / 1.G APB Engine Motronic Multiport Fuel Injection System Servising Owner's Guide

24-27

Idle speed, checking


Test conditions

No leaks in exhaust system
Coolant temperature at least 80 C

Electrical consumers switched off (radiator
fan must not run during the check)
A/C switched off
Pressure gauge not connected
Selector lever in position P or N (vehicles
with automatic transmission)

Checking idle speed

Notes:
The idle speed cannot be adjusted.
The idle speed is tested during the basic setting
of the engine.
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During the basic setting of the engine the A/C
compressor is automatically switched off and
the EVAP canister purge regulator valve is
closed.
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24-28

- Check DTC memory Page 01
-15
. The DTC
memory must be clear. If necessary, repair any
malfunctions and erase the DTC memory.
Switch off the engine, then start up again. Take
vehicle for a test drive and check DTC memory
again to make sure it is clear.

- Run engine at idle speed.

CAUTION!

The electric radiator fan should not be
running. Rapid data transfer
HELP
Select function XX

Indicated on display
- Press buttons -0- and -4- to select function "Basic Setting" and confirm
entry with -Q- button.
Basic settin
g
Input displa
y group number XXX

Indicated on display
- Press buttons -0- -5- and -6- to select "Display group number 056" and
confirm entry with -Q- button.
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24-29
Notes:
System in Basic Setting 56
1
2
3
4

Indicated on display: (1 - 4 display zones) - Check whether the engine speed shown in display field 1 (actual
engine speed) is within the specified tolerance range (750 - 850 RPM).

Display fields

1 2 3 4
Display Group 056: Idle speed stabilization with engine idling at operating temperature
Display
xxx RPM
xxx RPM x.x % xxxxxxx
Indicates
Engine speed (actual)
Engine speed
(specified) Idling speed control-
torque change Operating conditions
Specified
value 750 -850 RPM
800 RPM x.x % 0 0 0 0 0
Note
If readout does not match
Specified value Page 24
-31

Relevance of figures
Page 24
-32

The value shown in display field 1 is the actual engine speed.
The value shown in display field 2 (specified engine speed) is a theoretical value calculated by the engine control module.
See note on next page:
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24-30

When the engine is idling the engine control
module tries constantly to adjust the actual
engine speed so that it matches the specified
value.
This means that the actual engine speed when
idling should always be approximately the same
as the specified engine speed.
Display fields 3 and 4 provide additional
information which is not relevant when checking
the idle speed.

-
Press button.

- Press buttons -0- and -6- to select function "End
Output" and confirm entry with -Q- button.

- If readout does not match Specified value, check
DTC memory again.

- If DTC memory was erased, generate readiness
code Page 01
-105
.
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24-31

If the idle speed is too high or too low, or if
the engine does not idle smoothly, and there
are no malfunctions stored in the DTC
memory, carry out the following tests
(marked with dots):

Check intake system for un-metered air (air
leaks) Page 24
-76
.

Check Throttle Valve Control Module
Page 24
-139
.

EVAP canister purge regulator valve
constantly open, check Page 24
-134
.

Adaptation of Throttle Valve Control Module
Page 24
-146
.
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24-32
Relevance of figures in 5-digit readout in Display Group 056 x
x
x
x
x
Display field 4
0 A/C compressor off/on
0 = A/C compressor off
1 = A/C compressor on
0 Gear selector lever in P or N
0 = Gear selector lever in P or N
1 = Gear selector lever in 2/3/4/R/D
0 Climate Control readiness
0 = Minimum heating or cooling output
1 = Maximum heating or cooling output
0 Not used
0 Not used
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24-33

Fuel pressure regulator and residual
fuel pressure, checking


Requirements

Fuel pump relay OK
Fuel pump OK
Fuel filter OK
Battery voltage at least 11 V

Note:
The fuel pressure regulator regulates the fuel
pressure according to intake manifold pressure.
This ensures that the drop in pressure at the
injectors remains the same throughout all engine
speed and engine load ranges.

WARNING!

Fire hazard! The fuel system is pressurized.
Before loosening hose connections or
opening the test connection (to measure fuel
pressure), place a cloth around the
connection. Then release pressure by
carefully pulling off the hose or cap.
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24-34

Testing system pressure

Note:
If fuel flows out at the vacuum connection on the fuel pressure regulator
during the following pressure test, fit a new fuel pressure regulator. - Connect pressure gauge VAG 1318 to supply pipe using adapters
1318/7, 1318/8 (pressure hose) and 1318/15.
- Disconnect vacuum hose between fuel pressure regulator and intake
manifold at fuel pressure regulator end; seal off end of hose.
- Start engine and run at idling speed.
- Measure fuel pressure.
Specified value: approx. 3.8...4.2 bar
- If fuel pressure does not match specification, install a new fuel
pressure regulator for test purposes and repeat pressure test.
- If fuel pressure still does not match specification, check fuel pump and
supply pipe for damage (e.g. pinching) and replace if necessary.
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24-35

- If pressure is higher than specification, check
return pipe for damage (e.g. pinching) and
renew if necessary.

Note:
During the following test, do not allow the engine
to run for too long with the vacuum hose
disconnected, otherwise the increased fuel
pressure will enrich the air/fuel mixture and may
cause the lambda control limits to be exceeded.
This would be stored as a fault in the fault
memory.

- Start the engine and run at idling speed.

- Switch off electrical consumers (air conditioner
etc.).

- Re-connect vacuum hose to fuel pressure
regulator and observe drop in pressure on
pressure gauge.
Pa
ge 40 of 90 Motronic Multi
port Fuel In
jection
(MFI
) system, servicin
g
11/22/2002 htt
p://127.0.0.1:8080/audi/servlet/Dis
play?action=Goto&t
yp
e=re
pair&id=AUDI.B5.FU04.24.1