Replacing spark plugs (petrol models) (Opel Astra H)

Caution: The electronic ignition system generates very high voltage! Be careful and take all necessary precautions when servicing any components of the system, including not only the main (ignition module), but also related items such as spark plug connectors, tachometer and other equipment!

1. The correct functioning of the spark plugs largely determines the efficiency of the engine output. It is important that the engine is equipped with spark plugs of the type specified by the manufacturer (see Specifications). Attempts to "improve" the engine by installing more expensive and seemingly better spark plugs will most likely lead to the opposite result. On a serviceable engine, the need for unscheduled maintenance of spark plugs arises extremely rarely; do not unscrew the spark plugs for inspection without necessity. To avoid accidental damage to the electrodes, do not service or clean the spark plugs without using special equipment.

2. To replace the spark plugs, you need a special spark plug head (16 mm) complete with an extension, cardan joint and torque wrench (see accompanying illustration). Using a torque wrench will help ensure that the correct amount of tightening force is applied to the spark plugs.

Caution: Use a spark plug wrench with an elastic insert to prevent damage to the spark plug insulator!

3. All models covered in this Manual are equipped with an ignition module. It is installed between the camshaft housings, directly above the spark plugs (see accompanying illustration).

Caution: All spark plug replacement work should only be performed on a cold engine (engine temperature can be touched by hand) — otherwise, when removing the spark plugs on a hot engine, the internal thread of the spark plug installation hole on the cylinder head may be damaged.

4. Before removing the module on 1.8L models, remove the engine cover (see Chapter 2), and on models with a working volume of 1.6 liters, separate the cable channel from the cylinder head. Disconnect the electrical wiring from the ignition module and remove the module cover in the direction indicated by the arrow (see accompanying illustration).

Note: The direction of the arrow may vary depending on the model.

Unscrew the fastening screws, screw special handles into the central threaded holes of the module, or, if they are not available, a pair of long bolts of a suitable diameter with the appropriate thread pitch, and remove the module from the cylinder head.

Note: These handles are also used to prevent burns to your hands when removing the ignition module on a hot engine.

5. The spark plugs are deeply recessed into the spark plug recesses, so you will need a key extension to unscrew them (see accompanying illustration). After placing the head on the spark plug, connect the drive and, carefully turning the crank counterclockwise, unscrew the spark plug.



6. Check the removed spark plug with state map, which will allow you to qualitatively assess the general condition of the engine.

7. Checking the condition of the spark plugs gives a good idea of the engine condition. If there are no traces of any deposits on the insulator of the central electrode, this indicates that the air-fuel mixture is too lean, or that an excessively "hot" spark plug is used (heat dissipation from the insulator to the housing on "hot" spark plugs occurs much less intensively than on "cold" ones),



8. The presence of black carbon deposits on the electrodes indicates that the mixture is too rich, and if the carbon deposits also have an oily consistency, you should also consider a more detailed assessment of the degree of wear of the internal components of the engine.

9. A golden or grey-brown coating on the insulator confirms the engine is in good condition and the air-fuel mixture is correctly configured.

10. Modern engines use different types of spark plugs. Multi-electrode spark plugs are widely used (see accompanying illustration), which have increased wear resistance and reliability. The installation of interelectrode gaps on such spark plugs is carried out at the manufacturer and, as a rule, does not require any adjustments. If necessary, the installation of interelectrode gaps should be carried out in accordance with the instructions of the spark plug manufacturers.



11. The measurement of the interelectrode gap is performed using a special wire-type probe (see accompanying illustration 22.11a). When adjusting, only the side electrodes should be bent - attempts to deform the central electrode are fraught with irreversible damage to the insulator. If a blade-type feeler gauge is used to measure the spark plug gap, the gap can be considered adjusted correctly when the blade of the feeler gauge passes into it with slight resistance (see accompanying illustration 22.11b).







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12. Before installing the spark plug, make sure that the threads on the body and the outer surface of the spark plug are well cleaned.

13. If, upon inspection of the spark plug, damage to the threaded connection is found, the spark plug must be replaced, and if the thread in the cylinder head is damaged, it is necessary, without removing the head, to cut a new thread using a special tool for a special adapter sleeve that is screwed onto a standard spark plug.

14. Thread one of the new spark plugs into the appropriate hole in the engine by hand. After making sure that the spark plug is not twisted in the threads, tighten it to the required torque (see Specifications). To make the spark plug installation procedure easier, pull a piece of flexible fuel hose over its tail (see accompanying illustration) in order to eliminate the possibility of thread stripping, since the slightest biting will simply cause the hose to start turning. Proceed in a similar manner to install all the remaining spark plugs.





15. Install the ignition module and tighten its fasteners to the required torque (8 Nm).

Note: On 1.6L engines, the 4 ignition module gaskets must also be replaced.

Replace the cover and connect the module plug. Depending on the engine model (see paragraph 4) install the cable channel on the cylinder head and install the engine cover.