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
   - System of injection Mono-Motronic
      Operating procedure
      Malfunctions and independent diagnostics
      Independent repair
      Visual check
      Check of separate elements
      Check of the 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 Digifant
   + System of injection 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 electrical system
+ System of ignition
+ Lighting
+ Signaling devices
+ Devices and auxiliary devices
+ Heating and ventilation
+ Body elements
+ Search of malfunctions
+ Specifications

Operating procedure

Launch of the cold engine: from the sensor of temperature of cooling liquid the control unit obtains 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 the 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 at the same time the decrease in frequency of rotation arising because of inclusion powerful потребителй the current which is completely turned out in one party of the amplifier of the steering mechanism which is switched on the worker of position of the automatic transmission or the switched-on conditioner. It occurs by means of change of the moment of ignition.

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

Lambda regulation: when dispensing fuel the ratio of fuel/air l = 1 is considered. Constant 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 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 the mode of full loading. Therefore at mix there is in proportion more fuel. Informs a potentiometer on the provision of a butterfly valve. However at enrichment of gas mixture in the mode of full loading the signal a lambda probe is ignored.

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

Restriction of frequency of rotation of the engine: in case of excess of the maximum frequency of rotation the control unit turns off access of fuel for ensuring protection of the engine. Restriction of frequency of rotation cannot happen by shutdown of ignition 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, then the system of injection Mono-Motronic still continues to work normally. The so-called spare indicators which are already written down in memory are at the disposal of the control unit. 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 the insufficient power or bad starting properties.