BMW 3 Series E30
since 1983-1994 release
Repair and operation of the car
+ 1. Maintenance instruction
+ 2. Maintenance
+ 3. Engine
+ 4. Cooling system
+ 5. Heating and ventilation
+ 6. Fuel system
- 7. Exhaust system
+ 7.1.2. Exhaust system of cars 318i
- 7.2. System of decrease in toxicity of exhaust gases
7.2.2. Self-diagnostics of system of injection of Motronic
7.2.3. Processor block (ECU block)
7.2.4. Sensors of system of automatic control of the engine
7.2.5. System of compulsory ventilation of a case (PCV system)
7.2.6. System of catching of vapors of gasoline (EVAP system)
7.2.7. Catalytic converter
+ 8. Transmissions
+ 9. Coupling
+ 10. Brake system
+ 11. Running gear
+ 12. Body
+ 13. Electric equipment
+ 14. Useful tips
Sensor of temperature of cooling liquid
The sensor represents a thermistor (resistor which size of resistance depends on temperature). In process of reduction of temperature of the sensor its resistance increases and vice versa.
The sensor of concentration of oxygen in exhaust gases
Oxygen sensor socket
The oxygen sensor socket on models 325i 1986-88 of.
The sensor traces the content of oxygen in exhaust gases and generates output tension from 0,1 B (high content of oxygen, grown poor mix) to 0,9 B (small content of oxygen, enriched mix). The changing output tension from sensors moves on an electronic control unit which defines a ratio of oxygen and fuel in gas mixture. The control unit regulates a ratio of air/fuel in mix by a task of time of an open condition of nozzles. At a ratio of 14,7 parts of air to 1 part of fuel in initial mix the content of harmful substances in exhaust gases minimum, at such ratio converter purifies gases with maximum efficiency. An electronic control unit together with the sensor of oxygen provide maintenance of composition of gas mixture just at the specified level.
Oxygen sensor heater relay
If temperature of the sensor of concentration of oxygen is lower than normal working temperature, i.e. 320 °C, then tension on the sensor is absent. Therefore until the engine does not get warm, on an electronic control unit of a signal from the sensor of oxygen does not arrive and the block works in the mode of the opened cycle (preparing gas mixture automatically).
If after warming up of the engine, or not less than 2 minutes of operation of the engine later, tension on the sensor not of a prevyshayea 0,45 B at a speed of rotation of the engine not less than 1500 rpm, then the control unit brings a refusal code in memory.
If the sensor or its chain are faulty, then the electronic control unit works in the mode of the opened cycle, i.e. the block doses fuel according to the programmed value on its entrance, but not according to an oxygen sensor signal.
The correct operation of the sensor depends on the following conditions:
1. Electric: low voltage generated by the sensor very strongly depends on a condition of connections with wires.
2. Supply of external air: sensor is arranged so that air circulates in its internal space. Every time at removal or installation be convinced of purity of air channels of the sensor.
3. Working temperature: signals from the sensor do not arrive on an electronic control unit until temperature of the sensor does not reach about 300 °C. This factor should be considered at assessment of serviceability of the sensor.
4. Qualities of gasoline: use of unleaded gasoline is an essential condition of the correct operation of the sensor. Fill the car only with unleaded gasoline.
Besides the conditions stated above, at service of the sensor it is necessary to follow the following rules:
1. The flexible conductor and the socket of the sensor of oxygen are non-demountable and are not disconnected from the sensor. Damage or a separation of the flexible conductor or the socket can have an adverse effect on serviceability of the sensor.
2. Hit of dirt, lubricants and other foreign components on the socket or on the tower isolation center of the sensor is not allowed.
3. It is forbidden to wipe the sensor with all types of cleaners.
4. It is forbidden to drop the sensor or to handle carelessly it.
5. You watch correctness of installation of a silicone cover of the sensor to avoid melting of a cover because of which the failure of the sensor is possible.
Purpose of conclusions on the sensor of content of oxygen
The sensor represents 2 couples of contacts. Idling one couple of which is normally closed, and another – is opened. Near full opening of the gate the second couple of contacts becomes isolated. At an intermediate position of the gate both couples of contacts are opened. Break in chains or weakening of contacts of the sensor of a butterfly valve can cause spontaneous injection of fuel that is the reason of unstable operation of the engine idling.
Air stream measuring instrument
Sensors of system of ignition
The procedure for test, removals and installations is described in subsection 188.8.131.52.