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28 - Ignition system
1 - Testing ignition system
1.1 - Testing ignition system
1.2 - General notes on ignition system
◆ The engine control unit is equipped with self diagnosis.
◆ For trouble-free operation of the electrical components a voltage of at least 11.5 V is necessary.
◆ During some of the tests it is possible that the control unit will detect and record a fault. The fault memory
must therefore be interrogated and if necessary erased when all tests and repair work have been completed.
◆ After completing fault finding, repairs or component tests, it is possible that the engine will start, run for a
short period and then cut out. If this happens it may be that the immobilizer is blocking the engine control
unit. In such cases the fault memory must be interrogated and if necessary the control unit must be adapted.
1.3 - Safety precautions
To prevent injuries to persons and/or damage to the fuel injection and ignition system, the following must be
noted:
◆ Do not touch or disconnect ignition wiring when the engine is running or being turned at starter speed.
◆ The ignition must be switched off before connecting or disconnecting injection or ignition system wiring or
tester cables.
◆ In order to run the engine at starting speed without actually starting it (e.g. to test compression), unplug the
connectors from the output stages of the ignition coils and from all the injectors. After completing the work,
interrogate and erase the fault memory.
◆ The ignition must always be switched off when cleaning the engine.
◆ Always switch off the ignition before connecting or disconnecting the battery, otherwise the engine control
unit may be damaged.
1.4 - Technical data for ignition system
Engine code letters
AQD (2.8ltr. /5V/142 kWwith secondary air system)
APR (2.8ltr. /5V/142 kW without secondary air system)
Idling speed
Not adjustable - controlled by the idling speed
stabilisation
650 ... 750 rpm
Engine speed limited
- by closing throttle valve
- by shutting off injectors
approx. 6600 rpm
approx. 6800 rpm
Ignition timing is determined by the control unit.
Ignition timing cannot be adjusted.
Ignition system
Dual-spark system with three coils
Spark plugs
Tightening torque 30 Nm
Firing order
1-4-3-6-2-5
Audi A8 1994 ➤
Motronic injection and ignition system (6-cylinder) - Edition 02.1999
94
28 - Ignition system
