Spark plugs and the entire ignition system as a whole are matched to this engine, and this helps to reduce the amount of harmful substances in the exhaust gases. To avoid engine failures, reduction of its power, deterioration of acceleration, increase in the content of harmful substances in exhaust gases and interference with radio reception, only spark plugs recommended by Volkswagen for this engine should be used. Particularly important characteristics of candles are the number of electrodes, glow number and, in some cases, the ability not to interfere with radio reception.
Proper functioning of spark plugs is one of the most important conditions for the efficient operation of the engine. It is essential that only the specified type of spark plugs be fitted to the engine. With a good engine, cleaning spark plugs is a rare operation.
Installing new spark plugs after a short run (about 1000 km), it is advisable to unscrew them, marking the cylinder number, and carefully examine the condition of the insulators. With the right glow number and the optimal composition of the mixture and the ignition timing, the insulator will be light brown, brown or light gray. Multi-colored deposits on the insulator and electrodes indicate the presence of a large amount of additives in the fuel or engine oil.
Sometimes it may turn out that all candles of the same brand in different cylinders have insulators of different colors. There may be several reasons. As a rule, the air-fuel mixture and anti-knock additives are unevenly distributed throughout the cylinders.
There are engines with different compression ratios for each of the cylinders. Well, between engines of the same model, the compression ratio sometimes differs by a whole unit. Due to the deviation from technological processes, materials, etc., among candles of the same brand, there is also a large spread in actual glow numbers. With a large difference in the condition of the candles, it is sometimes necessary to install candles with different glow numbers even in the same engine. In order to always have a reserve for the glow number in various operating conditions, it is advisable to have two sets of candles and install colder ones in summer, and in winter "hot".
Withdrawal
To unscrew the spark plugs, you must use a 16 mm wrench, for example, HAZET 900 A KF, HAZET 4766-1 or a 3122V spark plug wrench from AUDI.
Replace spark plugs with a cold or warm engine. If the spark plugs are removed while the engine is hot, the spark plug threads in the cylinder head can be damaged.
Switch off the ignition.
4 cylinder engine
The replacement of candles on an 8-cylinder engine and a 2.7 liter engine is carried out in a similar way.
Unscrew the screws and remove the upper engine cover (see fig. 1.22).
Disconnect the electrical connectors from the ignition coils (see fig. 1.23).
Unscrew the ground bus from the cylinder head.
Unscrew the two mounting bolts and remove the ignition coils by pulling them up from the spark plugs (see fig. 1.23).
6 cylinder engine
Unscrew, remove from the bracket and move aside the expansion tank together with the hoses connected to it.
Unscrew the screws and remove the upper engine cover (see fig. 1.24).
For ease of installation, mark the spark plug wires with numbers 1 to 4.
Disconnect the spark plug electrical connectors. Use special tongs for this, eg HAZET 1849-1.
All engines
With a 16 mm wrench, for example HAZET 900AKF, unscrew the spark plugs.
Examination
Visual inspection of the working part of the spark plugs can show the condition of the engine. If the nose of the spark plug insulator is clean and white with no deposits, then the mixture is too lean. It also indicates that the spark plug is too hot, i.e. heat is slowly removed from the center electrode. If this is the case, then it is necessary to adjust the composition of the fuel mixture or replace the spark plug.
If the nose of the insulator is covered with a black coating, then this indicates that the mixture is too rich. If the plaque is black and oily, then this indicates engine wear and the need to check and repair it. If the nose of the insulator is covered with a light brown coating, then the mixture is optimal and the engine is in good condition.
The gap between the electrodes of a spark plug is of great importance, since too large and too small a gap changes the size of the spark, which leads to a decrease in engine efficiency. The gap must always comply with the technical requirements.
The clearance is checked with a feeler gauge, e.g. HAZET2147 MS (see fig. 1.25). AUDI A6 cars use spark plugs with three mass electrodes.
The gap between the spark plug electrodes is 1.0±0.1 mm.
New spark plugs have the correct gap between the spark plug electrodes. The gap can only be checked, not adjusted. If the gap is not as specified, the spark plug must be replaced.
Installation
Before installing the spark plug in the engine, check that the threads are clean and that all threads are intact.
Screw in the spark plugs, do not twist them, and tighten to 30 Nm.
4-cylinder engine. If damaged, replace seals between ignition coils and cylinder head. Install the ignition coils on the spark plugs and secure each of them with two bolts, tightening them with a torque of 10 Nm. Connect the electrical connectors to the ignition coils. Screw the ground bus to the cylinder head.
6-cylinder engine. Connect the wires to the spark plugs in accordance with the markings previously made. Install and secure the expansion tank.
Install and screw on the upper engine cover.
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