Table of contents: General information ↓ The engine does not start ↓ Cylinder misfires ↓ Other problems ↓
Warning! The voltages generated by the electronic ignition system are significantly higher than those generated by conventional systems. When working on the system, be extremely careful when turning off the ignition. Those with an electronic pacemaker should stay away from ignition systems and testing equipment. Always turn off the ignition before working on the system.
General information
1. Most ignition system faults are caused by dirty electrical connections or breakdown of old or damaged insulation, especially in high humidity. If a fault has occurred in the engine management system, first of all check the condition of all contacts, connectors, wiring, cleanliness of the air filter, condition of spark plugs, condition of air ducts and crankcase ventilation hoses.
2. Outdated methods of checking ignition "for spark" (disconnecting the high-voltage wires one by one from the spark plugs) are not recommended not only because there is a high risk of getting a strong electric shock, but there is also a possibility of damaging the ignition coil or the ECU. You can check the condition of the wire and spark plug in operation by unscrewing the spark plug and attaching it to the ground with a crocodile clip from the cigarette lighter. It is very important to ensure good contact with the ground. Never try to carry out "diagnostics" by removing high-voltage wires on a running engine.
The engine does not start
3. If the engine does not turn over with the starter, or turns over very sluggishly, first check the condition of the battery and the starter. Connect a voltmeter between the battery terminals (connect the positive probe of the voltmeter to the positive terminal of the battery), turn off the ignition by disconnecting the wiring connector from the ignition coil. Rotate the engine with the starter for no more than 10 seconds, measure the voltage at the battery terminals. If the voltage drops below 9.5 V, first check the condition of the battery, starter and charging system - see chapter 5A.
4. If the engine turns over as expected but does not start, check the ignition system by connecting a strobe light (according to the manufacturer's instructions) and turning the engine with the starter. If the stroboscope flashes, it means that the current is reaching the spark plugs via the high-voltage wire, which must be removed and checked. Check the fuel system as described in the relevant section chapters 4. If the strobe light does not flash, check the high-voltage wires - see chapter 1A.
5. On models without a distributor, check the condition of the high-voltage wires and the ignition coil as described in paragraph 3 of this chapter.
6. If no spark is detected, then the fault may lie in the engine management system. Contact your Audi/VAG dealer for assistance.
Cylinder misfires
7. Irregular misfires indicate possible unreliability of connections in the low-voltage part of the ignition system or a fault in the high-voltage circuit.
8. Turn off the ignition, check the reliability and cleanliness of the contacts of all ignition system connectors.
9. Make sure the high-voltage wires and ignition coils are clean. Check the condition of the spark plugs (if necessary, by replacing with known good ones) distributor cap, its carbon and runner (if provided).
10. Regular misfires indicate a faulty spark plug, high-voltage wire, loss of compression in one of the cylinders, or a faulty fuel injector.
11. If there is no high voltage on one particular wire, the fault may be in the wire itself or in the distributor cap (if such is provided). If there is high voltage on all wires, check the condition of all spark plugs.
Other problems
12. If the cause of the malfunction cannot be determined, contact a dealer who has specialized diagnostic equipment for this purpose.
(This publication is borrowed from the resource: «AUDImanual.ru»)