Audi 80/Avant (B4)

since 1991-1995 of release

Repair and car operation



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
- Injection system
   - System of injection of Mono-Motronic
      Operating procedure
      Malfunctions and independent diagnostics
      Independent repair
      Visual check
      Check of separate elements
      Check of a mode of idling and analysis of exhaust gases
      Check of catalytic converter and lambda probe
      Hummock drive of "gas"
      List of malfunctions
   + System of injection of Digifant
   + System of injection of KE-III-Jetronic
   + Systems of injection of MPI and MPFI
+ Coupling
+ Transmission and transmission
+ Suspension bracket and steering
+ Brake system
+ Anti-blocking system of brakes
+ Wheels and tires
+ Body electrosystem
+ ignition System
+ Lighting
+ Signalling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ body Elements
+ Search of malfunctions
+ Specifications



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Operating procedure

Start-up of the cold engine: from the sensor of temperature of cooling liquid the control unit receives information on engine temperature. Than the engine is colder, especially the injection period for creation of the starting mix enriched with fuel is long.

Warming up phase: the sensor of temperature reports about gradual warming of cooling liquid by means of changing indicators of resistance to the control unit.

Idling: the switch of a signal of idling informs the control unit on this operating mode. The regulator of provision of a butterfly valve regulates turns of idling and counterbalances thus decrease in frequency of the rotation, arising because of inclusion powerful потребителй the current which has been completely turned out in one party of the amplifier of the steering mechanism, included the working provision of an automatic transmission or the switched-on conditioner. It occurs by means of change of the moment of ignition.

Normal operation: the control unit receives information on operation of the engine thanks to impulses of frequency of the rotation, proceeding from the Hall sensor, and to resistance indicators from a butterfly valve potentiometer (the provision of a butterfly valve). From this the control unit does conclusions about a condition of load of the engine and measures through a vpryskny nozzle necessary amount of fuel to arriving air.

Lambda regulation: when dispensing fuel the fuel/air l ratio = 1 is considered. Continuous change of the enriched and grown poor mix does possible optimum work of catalytic converter.

Acceleration: thanks to signals from a potentiometer the control unit distinguishes sharp pressing an accelerator pedal as acceleration process owing to what the mix "is immediately enriched".

Full loading: in the provision of full "gas", or to tell more precisely, at the provision of a butterfly valve about 72,5 ° the control unit provides enrichment of gas mixture in a mode of full loading. Therefore at a mix there is in proportion more fuel. On the provision of a butterfly valve informs a potentiometer. However at enrichment of gas mixture in a mode of full loading the signal a lambda probe is ignored.

Mode of compulsory idling (movement nakaty): at movement under a hill with the released pedal of "gas" the system of injection of Mono-Motronic saves fuel and disconnects fuel access as soon as the engine reached working temperature. The control unit distinguishes this operational condition on the released pedal of "gas" (a butterfly valve potentiometer), messages from the sensor of temperature of cooling liquid and frequency of rotation of the engine over 1500-1900 rpm (the Hall sensor).

Restriction of frequency of rotation of the engine: in case of excess of the maximum frequency of rotation the control unit disconnects fuel access for ensuring protection of the engine. Restriction of frequency of rotation cannot occur by ignition shutdown because in this case not burned down fuel will get to catalytic converter. It can lead to dangerous temperature increase and, thereby, to long damages of catalytic converter.

Work in emergency situations:
if the signal from one of suppliers of information does not come absolutely or has senseless size, the system of injection of Mono-Motronic still continues to work normally. At the disposal of the control unit there are the so-called spare indicators which have been already written down in memory. The similar spare indicator, of course, cannot consider many service conditions, but the car after all remains mobile. The driver can distinguish lack of a signal from the sensor on insufficient capacity or bad starting properties.