Audi 80/Avant (B4)

since 1991-1995 release

Repair and operation of the car

Audi 80/Avant
+ Technical specification
+ Engines
+ System of production of the fulfilled gases
+ Cooling system
+ Fuel tank and fuel pump
+ Air filter and airintaking channels
+ System of injection
+ Coupling
+ Transmission and transmission
+ Suspension bracket and steering
+ Brake system
+ Anti-blocking system of brakes
+ Wheels and tires
+ Body electrical system
- System of ignition
   Various systems of ignition
   Principle of work of ignition
   Executive body
   System "brain"
   Impulses for the control unit
   Regulation on a detonation
   Security measures during the work with system of ignition
   Repair of system of ignition
   Diagnostics of system of ignition
   Ignition distributor
   Sensor of detonation combustion
   Elements of high voltage
   Replacement of spark plugs
   Spark plugs
   Check of the moment of ignition
+ Lighting
+ Signaling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ Body elements
+ Search of malfunctions
+ Specifications

Replacement of spark plugs

The plan of servicing provides each 30 000 km replacement of spark plugs. This interval is represented to us real and you should not prolong it. It is necessary to watch closely serviceability of system of ignition, especially on the cars equipped with catalytic converter, – we already spoke about it. But nevertheless it is worth looking at the removed candles attentively: it is provided below what can tell you a deposit on a spark plug about.

By the way, if you removed candles for control in an interval between replacements: hands it is better not to clean them. It will damage an insulating layer of an average electrode of a spark plug (steatite). However you can check a gap between electrodes.

Removal of spark plugs


  1. To pull together tips of spark plugs from contact probes of candles. Not to pull wires!
  2. To turn out spark plugs and to put according to the sequence of cylinders that on a condition of a candle it was possible to draw conclusions on a condition of the corresponding cylinder.
  3. If candles are difficult turned out, do not use force, otherwise a thread in a head from light alloy can be stripped.
  4. Warm up the engine and now turn out candles.
  5. At installation it is impossible to roll cold candles in the hot engine, then they will be difficult to be turned out.
  6. Spark plugs it is necessary to tighten the moment of 20 N • m. If near at hand there is no dynamometer wrench:
  7. To screw a candle to a prileganiye of a sealing ring – in this case it it is impossible to turn more neither a hand, nor a candle key without the use of force.
  8. Now, if you established new candles, tighten a candle key still approximately on a quarter of a turn.
  9. If you put already used candles, will be enough if you turn a candle key approximately on 15 °.

 Hints: in order that it is easier to screw and subsequently to turn out a candle, you can apply a little graphite from a soft pencil on a carving or a little copper lubricant. Oil or usual plastic lubricant lead to a spark plug prikipaniye in a carving of a head of the block of cylinders.

The defective carving of a spark plug is not a reason for despair at all! The workshop will put in this case the special carving plug (for example Heli-Coil insert).

Deposit on candles

Spark plugs in a sense of this word are witnesses of combustion in the engine. Appearance of spark plugs allows to define (deposit) whether the engine optimum works. Previously it is necessary to warm thoroughly the engine on the country road or the highway. Control after a short distance can lead to the wrong conclusions. Look at an insulator cone tip with an average electrode and side electrodes.

  • The tip of a cone of the insulator has gray or brownish color: well adjusted system of injection, the engine works economically.
  • Strong deposits: additives in engine oil or fuel, or the raised oil consumption can be the cause. Perhaps, it is necessary to change brand of oil or fuel.
  • Black sazheobrazny deposits: the spark plug because of frequent trips on short distances does not reach self-cleaning temperature, the wrong kalilny number.
  • The tip of a cone of the insulator has brown color: too early moment of ignition, does not function electronic regulation of the moment of ignition or the sensor of detonation combustion.
  • Traces of oplavleniye on an average and side electrodes: the kalilny ignition caused by deposits in the combustion chamber, superheated nozzles, the wrong moment of ignition which is brought down by the ignition moment, the faulty sensor of detonation combustion or an overheat of the engine.
  • The insulator cone is broken, in an initial stage it is distinguishable as a thin crack: the detonating combustion because of bad fuel, incorrectly adjusted ignition, the brought-down ignition moment, the faulty sensor of detonation combustion, insufficient cooling of the engine or impoverishment of mix because of hit of unaccounted air.
  • Oil layer on electrodes and an internal surface of a spark plug: the damaged piston rings, guides of valves or oil scraper caps of valves.
  • If on a surface of a spark plug there are no specified signs, however the engine is all the same slowly started or works with interruptions, the reason nevertheless can be covered in candles. Invisible cracks in the ceramic insulator can be filled during cold start with the condensed fuel because of what there is a leakage of a spark. Candles can refuse at operation though the spark is visible when the candle is removed.

Gap between electrodes

Mix of fuel and air, and also products of combustion make korrizionny impact on metal electrodes of spark plugs. And high voltage at a proskakivaniye of a spark pulls out parts of metal because of what in operation the gap between electrodes increases. The following indicators of a gap between electrodes of spark plugs are admissible:

  • 4-and 5-cylinder engines: 0,7 — 0,9 mm
  • 6-cylinder engines: 0,9 — 1,1 mm

By the three-electrode candlelight which are applied in Audi 80 the igniting spark can "choose to itself" respectively the shortest spark interval. Therefore it will hardly be required to turn in an electrode in addition.