Audi A4

since 1994 release

Repair and operation of the car

A4 Audi
+ Running gear
+ Regular servicing
+ Engines
+ Turbo-supercharging
+ System of an exhaust
+ Cooling system
+ Fuel tank and fuel pump
- Air filter and channels of absorption
   Dismantle of an insert of the air filter
   Purge of an insert of the air filter
   Replacement of an insert of the air filter
   Preliminary heating of the soaked-up air
   The switching inlet collector
+ System of injection
+ Coupling
+ Transmission and main transfer
+ Suspension bracket of wheels and steering
+ Brakes
+ Wheels and tires
+ Electrotechnical equipment
+ System of ignition
+ Lighting
+ Alarm equipment
+ Tools and devices
+ Heating and ventilation
+ body Details
+ Salon
Search of malfunctions
Technical characteristics

Preliminary heating of the soaked-up air

Six-cylinder engine

The device of automatic preliminary heating of the soaked-up air is from the entrance party of the case of the air filter. It is faced by a problem of the support of favorable air temperature which is soaked up by the engine.

For this purpose there is the following reason: at cold weather fuel and air mix is sated more if the soaked-up air moves the previously heated. The same amount of warm air occupies the bigger volume, than cold air. As the engine can soak up only certain amount of air, at the included preliminary heating a little less air arrives – mix becomes richer, fuel consumption increases. It is necessary for trouble-free operation of the engine only at low temperatures.


The gate of preliminary heating of the soaked-up air is adjusted by the thermostat which completely opens supply of warm air at a temperature of -20 °C. At temperature increase the gate is slowly closed until at a temperature of +5 °C is not closed completely.

Violations in work

If preliminary heating of air functions unsatisfactorily, it can lead to operational violations.

In a cold season:

  • Unstable idling after start of the cold engine at a warming up stage.
  • Bad switching, the engine it is inclined to interruptions.

In a warm season:

  • The lowered power, is not reached the maximum speed.
  • The increased fuel consumption.

Check of preliminary heating of air

Six-cylinder engine


  1. Dismantle a filter insert.
  2. Look in a hose branch pipe if it is necessary, take a lamp.
  3. Depending on surrounding temperature the air gate has to close supply of cold or warm air.