Audi 80/Avant (B4)

Since 1991-1995 of release

Repair and car operation

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

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

Removal of spark plugs

Deposit on candles

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

• The tip of a cone of an insulator has grey or brownish colour: well adjusted system of injection, the engine works economically.
• Strong adjournment: additives in engine oil or fuel, or the raised expense of oil can be the reason. Probably, it is necessary to change oil or fuel mark.
• Black сажеобразные adjournment: the spark plug because of frequent trips on short distances does not reach self-cleaning temperature, wrong калильное number.
• The tip of a cone of an insulator has brown colour: too early moment of ignition, does not function electronic regulation of the moment of ignition or the gauge of detonation combustion.
• Traces оплавлений on an average and lateral electrodes: калильное the ignition caused by adjournment in the chamber of combustion, перегретыми atomizers, the wrong moment of the ignition which have been brought down by the moment of ignition, the faulty gauge of detonation combustion or an engine overheat.
• The insulator cone is broken, in an initial stage is distinguishable as a thin crack: detonating combustion because of the bad fuel, incorrectly adjusted ignition, the brought down moment of ignition, the faulty gauge of the detonation combustion, insufficient cooling of the engine or pauperisation of a mix because of hit of not considered air.
• Oil layer on electrodes and an internal surface of a spark plug: the damaged piston rings, directing valves or маслосъемные caps of valves.
• If on a surface of a spark plug there are no specified signs, however the engine all the same is slowly started or works with faults, the reason nevertheless can be covered in candles. Invisible cracks in a ceramic insulator can be filled during cold start with condensed fuel because of what there is a spark leak. Candles can refuse at operation though the spark is visible when the candle is removed.

Backlash between electrodes

The fuel and air mix, and also combustion products render корризионное influence on metal electrodes of spark plugs. And the high voltage at проскакивании sparks pulls out metal parts because of what in operation the backlash between electrodes increases. Following indicators of a backlash 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

At applied in Audi 80 three-electrode candles the igniting spark can «choose to itself» accordingly the shortest spark interval. Therefore hardly it is required to turn in an electrode in addition.