To replace the spark plugs in a 92 kW engine, you need to disconnect the connector (1) on the final power stage and unscrew the final stage together with the ignition coils. The arrows show the screws. When installing, note the order of laying the wire: wire from the rear coil (2) goes to the 2nd cylinder (4); front coil wire (3) - to the 1st cylinder (5).
The maintenance plan calls for spark plug replacement every 60,000 km or every three years, whichever comes first. The time interval prevents the appearance of a defect due to aging at low mileage.
Audi has a very long service interval which can only be observed if the correct spark plug types are used. Therefore, there is no reason to lengthen it even more. Special attention should be paid to the working condition of the ignition system if the cars have a catalytic converter - we have already talked about this.
It is worth critically examining the dismantled candles: then you will read what he says «candle face».
If the spark plugs are sometimes unscrewed for inspection: it is advisable not to clean the spark plugs by hand. This will damage the insulating layer of the intermediate electrode of the spark plug (steatite).
Removing spark plugs
1. 1.8L engine and six-cylinder engine: Remove the engine cover.
2. Engine 1.8 l 92 kW: unscrew and remove the ignition coils with the final power stage; remove the spark plug connectors.
3. Engine 1.8 l 110 kW: unscrew and remove the individual ignition coils.
4. When dismantling the ignition coil connectors, do not pull on the wire, but grasp the connector itself.
5. Unscrew the spark plugs and put them in a sequence of cylinders so that you can draw conclusions about the condition of the candle of the corresponding cylinder.
6. If the candles sit very firmly, then do not use force, otherwise the threads of the candles in the cylinder head made of light metal can be torn off.
7. Warm up the engine and now unscrew the candles.
8. During installation, do not screw tightly cold candles into a heated cylinder head, otherwise they will then sit as if riveted.
9. Spark plugs must be screwed in 30 Nm. If there is no torque wrench at hand, then:
10. Screw in the spark plug so that the o-ring fits - it can no longer be screwed in without force, either by hand or with a spark plug wrench.
11. Now screw in the new spark plug with a special wrench exactly a quarter of a turn stronger.
12. A used candle may only be screwed in by approx. 15°.
The spark plugs must be tightened to 30 Nm. If you do not have a torque wrench handy: screw the spark plug so that the O-ring (arrow) fit - in this case, it cannot be tightened by hand or a key without the application of force. Now, if the spark plug is new, tighten it exactly a quarter of a turn with a wrench. If the candle was in use, then turn it with a key only about 15°, this is enough.
Tips: To increase the slip of the spark plug threads, you can scrape some graphite into the threads from a soft pencil or lightly lubricate them with copper-based grease. Oil or grease «bake» spark plug in the threads of the cylinder head.
«spark plug face»
Spark plugs are, to a certain extent, witnesses to the combustion process in the engine. By the appearance of the top of the candle («candle face») you can determine how optimally the engine works. Pre-warm up the car thoroughly on a rural road or on a motorway. Checking after driving a short distance may result in incorrect output. Look at the top of the insulator with the middle electrode and the side electrodes:
- The top of the insulator is light gray or brownish: correct installation of the injection system, the engine runs economically.
- Strong deposits: The cause may be additives in the engine oil or fuel, or increased oil consumption. Change brand of oil or fuel.
- Soot-like black deposits: due to frequent movement over short distances, the candle does not reach the self-cleaning temperature, incorrect glow number.
- Whitish top of insulator: Ignition timing too far to one side «advancing», the electronic ignition timing control or the knock sensor does not work.
- Fused areas on the center and ground electrodes: glow ignition due to deposits in the combustion chamber, overheated valves, incorrectly set ignition point, faulty ignition point adjustment or heat stagnation due to insufficient cooling.
- Destruction of the top of the insulator, initially visible as hairline cracks: detonation combustion due to poor quality fuel, incorrect ignition setting, defective ignition point adjustment, defective knock sensor, insufficient engine cooling or lean air-fuel mixture due to bypass air.
- A yellowish shiny layer on the top of the insulator: deposits formed due to additives in gasoline and engine oil, which, with a sharp full load on the engine, turned into a liquid state and became electrically conductive and, as a result, misfiring. When driving short distances for a week, you should not immediately put the engine under full load.
- A layer of oil on the electrodes and the inner surface of the candles: a defect in the piston rings, valve guides or valve stem gaskets.
- If any features are not noticeable in the appearance of the spark plug, but the engine does not start well or twitches, the reason may still be in the candles. When starting a cold engine, invisible cracks in the ceramic insulator can be filled with fuel condensate, which deflects the ignition spark. Under pressure, the candles can also fail, although in the dismantled state you can see how a spark jumps. Replace if in doubt.
Distance between electrodes
The fuel-air mixture and exhaust gases contribute to the corrosion of the metal electrodes of the spark plugs. And high voltage, when a spark jumps, tears off the smallest particles of metal from them, as a result of which the distance between the electrodes of the spark plugs increases over time. In the presence of spark plugs with three electrodes, the ignition spark can «find» the shortest way. Therefore, it is almost not necessary to bend the electrodes.
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