Attention! We recommend not to clean the removed spark plug manually. This will damage the insulation layer of the central electrode of the spark plug.
You can check the gap between the spark plug electrodes yourself.
1. Remove the high-voltage wire tips from the spark plugs.
2. Remove the spark plugs and arrange them in accordance with the order of cylinder operation. Subsequent inspection of the spark plugs will allow you to draw certain conclusions regarding the corresponding cylinder.
3. Do not apply significant force if the spark plugs cannot be unscrewed. You may damage the thread of the spark plug hole.
4. Warm up the engine and remove the spark plugs.
Warning! Do not install cold spark plugs on a hot engine. They will not be able to be unscrewed later, because in this case they will be seated as if on rivets.
5. Tighten the spark plugs to 20 Nm when installing. If it is not possible to use a torque wrench when installing the spark plugs, follow the following rule to install the spark plugs correctly.
6. Screw in the spark plug until the sealing ring touches the surface of the cylinder head.
Further tightening of the spark plug is impossible without applying a certain amount of force. In this position, tighten the new spark plug by about a quarter of a turn, and the used one by turning the key by about 15°.
Attention! To make the spark plugs easy to unscrew, apply a little graphite to their threads by crumbling a pencil lead, or lubricate them with a thin layer of copper grease. Lubricating the spark plug threads with regular grease or oil only makes things worse. In this case, the spark plugs stick to the threads.
If the thread in the spark plug hole has been stripped, then workshops in this case use a corresponding threaded sleeve, which is inserted into the spark plug socket.
The condition and appearance of the spark plugs can tell you quite a lot about the engine's performance. If the spark plugs are removed for this purpose, the engine should first be warmed up by driving a fairly long distance. Inspect the spark plug, paying particular attention to the central electrode insulator and the side electrodes.
- a) the central electrode insulator is grey or brownish in colour. The fuel injection system is well adjusted and the engine runs economically.
- b) a layer of deposits. This may be caused by additives in motor oil or fuel, as well as increased oil consumption. You can change the type of oil or fuel.
- c) black soot-like deposits. Due to the vehicle's use in short-distance driving mode, the spark plugs do not heat up to the self-cleaning temperature. Incorrect glow number of the spark plug.
- d) White color of the insulator. The ignition timing is too early. The electronic ignition control or the knock sensor is not working.
- d) melting of the central and side electrodes. Pre-ignition due to deposits in the combustion chamber. Overheating of the injectors, incorrectly set ignition advance angle, faulty electronic ignition control, defective knock sensor or overheating due to insufficient cooling.
- g) insulator fracture. At the initial stage, it appears as microscopic cracks. The result of detonation combustion due to filling with low-quality fuel, incorrectly set ignition timing, incorrect ignition timing, defective detonation combustion sensor, insufficient cooling or lean mixture due to air "sucking in".
- c) oil film on the electrodes and spark plug. Wear of piston rings, valve stems or oil scraper caps.
If the spark plug is outwardly normal, but the engine starts with difficulty, jerkily, then the spark plugs may still be the cause. Cracks in the ceramic insulator that are not visible when inspecting the spark plugs may fill with fuel condensate when starting a cold engine and the spark discharge may be diverted in a different direction. The spark plug may not fire as a result of the pressure that is generated, although it produces a spark when removed.
Nominal values of the gap between spark plug electrodes:
- four- and five-cylinder engines: 0.7-0.9 mm;
- six-cylinder engine: 0.9-1.1 mm.
The spark of the spark plugs with three side electrodes used in AUDI 80 cars "seeks out" the electrode with the minimum gap. For this reason, bending the electrode is practically not necessary.
When choosing spark plugs, there are some factors to consider:
1) Heat rating. The spark plugs installed must match the temperatures occurring in the combustion chamber. The heat rating is the temperature value that the spark plug can withstand.
2) Electrodes. AUDI 80 cars are equipped with spark plugs with three side electrodes.
3) Spark plug thread. The spark plug thread for A UDI80 vehicles should be 19 mm. Thread diameter is 14 mm.
4) The size of the hexagon on the spark plug under the key. For spark plugs installed on cars with 4- and 5-cylinder engines, the width of the hexagon is 20.8 mm, and for six-cylinder engines - 16 mm.
5) Sealing. The manufacturer of AUDI 80 cars recommends flat sealing spark plugs for all models. These spark plugs have a non-removable sealing ring.