Audi A4

since 1994 of release

Repair and car operation



A4 Audi
+ Running gear
+ Regular servicing
+ Engines
+ Turbo-supercharging
+ exhaust System
+ cooling System
+ Fuel tank and fuel pump
+ Air filter and absorption channels
- Injection system
   - System of injection of Motronic
      The major knots
      So the system of injection of Motronic functions
      Violations in work and self-diagnostics
      The self-help at injection
      Visual control
      Search of malfunctions in separate knots
      Check of idling and exhaust gases
      Check of exhaust gases (AU)
      Butterfly valve cable
      The help at malfunctions
   + System of injection of MPI and MPFI
+ Coupling
+ Transmission and main transfer
+ Suspension bracket of wheels and steering
+ Brakes
+ Wheels and tires
+ Electrotechnical equipment
+ ignition System
+ Lighting
+ Alarm equipment
+ Tools and devices
+ Heating and ventilation
+ body Details
+ Salon
Search of malfunctions
Technical characteristics





The major knots

Electronic control unit

The control unit in an electronic box via the mnogoshtyrkovy socket receives information:

  • starter, the plug 50 began also completion of process of start-up;
  • potentiometer of a butterfly valve, its situation at present;
  • the sensor of the Hall of system of ignition for adjustment of number of turns of the engine;
  • lambda probe in the catalytic converter for measurement of the content of residual oxygen in exhaust gases;
  • measuring instrument of a stream of soaked-up air;
  • the sensor of temperature of soaked-up air (only in a turbodvigatel in capacity of 110 kW);
  • the sensor of temperature of cooling liquid in a tube of supply of cooling liquid behind a head of the block of cylinders;
  • sensor of a detonation of I engines on the block at "detonation" combustion;
  • sensor of a detonation of II (only in engines with working volume of 1,8 l) also on the engine block for exact localization of detonation combustion.

On the basis of information on number of turns and pressure in an inlet collector the control unit counts duration of opening of the injectors putting in action by an electromagnetic way, and, respectively, amount of injected fuel. For this purpose in the order of the control unit the characteristics of the engine representing collection of data on all conceivable situations of the engine, about amount of fuel necessary for everyone situation and the corresponding moment of ignition are provided. The control unit can vary still characteristics after receipt of so-called correcting signals (for example, temperature of soaked-up air and cooling liquid).

Control unit butterfly valve

The control unit (2) systems of ignition/injection is in an electronic box at the left behind in an impellent compartment (in the so-called moistening tank). In an arm (1) near the control unit there is a place of the sensor of height for a turbodvigatel.


The control unit a butterfly valve in a turbodvigatel with working volume of 1,8 l: 1–butterfly valve lever; 2–junction point of power supply of the control unit (3) butterfly valve; 4–butterfly valve.


The control unit a butterfly valve in the engine with working volume of 1,6 l in principle is identical to the engine block with working volume of 1,8 l, though assembly situation at it another. By figures are designated: 1–a junction point to power supply; 2–butterfly valve lever.

In the so-called control unit a butterfly valve three separate knots known on other systems of injection as functional blocks are incorporated.

Butterfly valve. It is connected by a cable with a pedal in salon and doses out a stream of fresh air in the engine. The gas pedal is more pressed, the butterfly valve more strongly opens, at full gas it is open completely.

Butterfly valve potentiometer. The potentiometer of a butterfly valve defines the provision of a butterfly valve on given the moment in a range from idling (the butterfly valve is closed) to full gas (the butterfly valve is open completely). On the basis of its information the valve of stabilization of the idling, also integrated in a butterfly valve branch pipe becomes more active, there is a shutdown of draft or mix enrichment at full loading.

Valve of stabilization of idling. It lets in dosed-out additional amount of air absorption canals behind a butterfly valve at a stage of warming up of the engine, at complete turn of a servoupravleniye, at working climatic installation or the established step of automatic transfer. The raised stream of air in the direction of the soaking-up pipeline is distinguished by a measuring instrument of a stream of fresh air and as a result causes increased supply of fuel. Thus, there is a decrease in the raised friction in not heated-up engine or at raised load of the engine for the account сервонасоса, the compressor of climatic installation or automatic transfer which take away capacity from the engine.

Pressure regulator

The regulator of pressure (1) fuel is connected to a butterfly valve branch pipe means of a vacuum hose (2). It regulates pressure in system by increase or fall of a retsirkulyatsiya of fuel.

It is in the distributor of fuel and regulates its pressure upon injectors. For this purpose information on level of the lowered pressure in an inlet collector is transferred to it. Idling at the closed butterfly valve and very low pressure it holds lower pressure. With pressure drop at raised load of the engine the regulator of pressure increases pressure of fuel. The fuel pump creates much more high operational pressure, but by means of a pressure regulator return of gasoline to a fuel tank respectively increases or decreases.

Injection valves

Valves of injection (4–7) settle down in the direction of travel on the left side of a head of the block of cylinders in an inlet collector. Further by figures are designated: 1–regulator of pressure of fuel; 2–a submitting gasoline pipe line; 3–distributive tube of fuel.


On this model in a cut it is visible that each valve of injection (3) makes injection in soaking-up pipe (4). Fuel arrives to it from a distributive tube (1), signals for injection go through cable connection (2) to the control unit.

At each turn of the crankshaft they inject gasoline into the absorption canal in front of the inlet valve of the corresponding cylinder – duration is defined by the control unit.

The sensor of temperature of soaked-up air

At a turbodvigatel in capacity of 110 kW it is in an airintaking hose and can precisely measure the air temperature, submitted by a turbokompressor. Information on temperature arrives in the control unit in the form of resistance size. It is used for an optimum dosage of fuel. The hot turbokompressor depending on a working condition strongly heats up soaked-up air.

The sensor of temperature of cooling liquid

The temperature of cooling liquid is used at management of several functions of injection: at enrichment of a fuel and air mix during start of the cold engine, poststarting enrichment (on all range of temperatures), at enrichment during accelerations and draft shutdown. Information on temperature of cooling liquid is transferred in the control unit also in the form of resistance size. He counts the correct time of injection which in the heated-up engine makes from 2 to 8 ms. This size can increase almost for 70 % when the temperature goes down to the Arctic level of-25 °C.

Measuring instrument of a stream of fresh air

In a stream of soaked-up air there is an electrocarrying-out plate which is warmed up in the electroway. Depending on amount of soaked-up air its stream which more strongly or more poorly cools a plate changes. Change of temperature causes change of electric resistance of the conductor. This measured size is used by the control unit.

Behind on the right in an impellent compartment of the naturally aspirated engine with working volume of 1,6 and 1,8 l there is a measuring instrument of a stream of fresh air (1), priflantsovanny to the case of the air filter. Figure «2» showed the connection socket. In a turbodvigatel with working volume of 1,8 l the measuring instrument of a stream of fresh air settles down inside in the case of the air filter.