Spark Plug Inspection and Replacement

GENERAL INFORMATION EVERY 60,000 KM (37,000 MILES)

CAUTION

Replace spark plugs only on a cold or slightly warm engine. If the plugs are removed from a hot engine, the threads in the light-alloy cylinder head may be damaged.

PROCEDURE

1. Before starting work, prepare all necessary tools. Some spark plug manufacturers supply special tools for measuring spark plug gap.

You will need the following for this work:

– 16 mm spark plug socket, for example, HAZET 900AKF. AUDI workshops use spark plug wrench 3122B for this. – Additionally, it is recommended to obtain special pliers, for example, HAZET 1849, which make it easier to unscrew spark plugs. AUDI uses assembly wrench 3277A for this. – 4 spark plugs. Required spark plugs are listed in the Specifications.

2. The best method of replacing spark plugs is to buy new spark plugs in advance, adjust their gap, and replace each spark plug one at a time. When buying spark plugs, it is very important to select the ones specified for your vehicle's engine. Information on them can be found in the Specifications in the Engine Electrical System Chapter.

3. With new spark plugs at hand, allow the engine to cool down completely before starting to remove the old ones. During this time, inspect the new spark plugs for defects and check the spark plug gaps.

4. Check the spark plug gap by inserting a feeler gauge of the required thickness between the electrodes at the tip of the spark plug. The gap must match the value given in the Specifications. The gauge wire should only just touch each electrode. If the gap is not within specification, carefully bend the curved part of the electrode using a notched gap tool until the required gap is obtained.

CAUTION

When adjusting the gap of a new spark plug, bend only the base of the ground electrode, not its tip. If the ground electrode is misaligned with the centre electrode, align them using a notched gap tool. Check the porcelain insulator for cracks, which indicate that the spark plug must be replaced.

5. Switch off the ignition.

6. Engine 1.6 L: Remove the bolts securing and remove the engine cover.

7. Engines up to 125 L hp: Disconnect the electrical connectors –2– from the spark plugs. Note: The illustration shows the engine of a different vehicle.

8. If possible, blow out the spark plug wells with compressed air so that dirt does not fall into the spark plug bores after the spark plugs are removed.

9. Engine 1.8 L/150 L hp: Remove the bolts securing and remove the engine cover.

10. Disconnect the ignition coil electrical connectors. To do this, pull up the locking clips.

11. Remove the bolts securing the ignition coils to the cylinder head and pull the coils up off the spark plugs.

CAUTION

Visually check the seals between the ignition coils and the cylinder head. If damaged, replace the parts.

All engines:

12. Unscrew the spark plugs using the appropriate spark plug socket. Take care

CAUTION

to ensure that the spark plug socket does not tilt, which may cause the ceramic insulator to break. Use a suitable socket, for example, HAZET 900AKF. AUDI workshops use spark plug wrench 3122B for this. Check

13. Compare the removed spark plug with the illustrations in Chapter 5; this will provide useful information about the general condition of the engine.

14. Check the electrode gap with a feeler gauge. The Audi A3 uses spark plugs with three ground electrodes. The required gap value is given in the Specifications.

CAUTION

New spark plugs usually have the correct electrode gap. If the thread of a spark plug is damaged, it must be replaced. A suitable tool and repair kit are available for this, for example from BERU. The old threaded hole can be drilled out using a special drill. The cylinder head does not need to be removed for this. After that, a new thread can be cut in the cylinder head and the spark plug installed using a special threaded insert. Threaded inserts seat securely and seal reliably.

15. To set the gap, bend the corresponding ground electrode. To do this, tap the side of the ground electrode. When bending, rest a small screwdriver against the edge of the thread. Never rest the tool on the centre electrode, as it may be damaged.

16. Apply a small amount of copper-based anti-seize compound to the thread of the new spark plug. Install the spark plug into the cylinder head and screw it in by hand until it seats, then tighten it using the spark plug socket. If possible, use a torque wrench to tighten the spark plug to ensure it is installed correctly. The spark plug tightening torque is given in the Specifications.

CAUTION

To prevent the spark plug from being screwed in cross-threaded, slide a short piece of rubber hose or plastic tube over its shank. The flexible tube works as a universal joint, allowing the spark plug to align with the spark plug bore. If the spark plug starts to tilt, the hose will slip on it, preventing the threads from being stripped.

17. Before connecting the high-tension (HT) lead to the spark plug, inspect it carefully.

18. Connect the lead to the newly installed spark plug, again using a twisting motion and holding the connector until it is fully seated on the spark plug.

19. Repeat the above procedure for the remaining spark plugs in sequence to avoid incorrect connection of the spark plug HT leads.

20. Engine 1.8 L 150 L hp: Install the ignition coils and tighten to 10 N·m. Connect the electrical connectors.

21. Install and secure the engine cover.