Genuine Audi 90 Mass Air Flow Sensor

Audi 90 Mass Air Flow Sensor Parts and Q&A

• Mass Air Flow Sensor
  078-133-471-AX
  Q: What is the function and testing procedure of the Coolant Temperature Sensors, Mass Air Flow Sensor, Oxygen Sensor and Throttle Position Sensor on Audi 90?

  A:

  The Multipoint injection system (MPI) has a fault memory which includes the fuel injection system and ignition system with a self-check procedure. In order to test the probe of the lambda, dislodge the wiring plug in its immediate vicinity to the inlet manifold and then attach a voltmeter to the probe's terminals, and start the engine to ensure that there is a voltage of 12VOLTS; otherwise, examine the circuit. In removing the lambda probe of the Exhaust Manifold, make sure that its threads have been covered with suitable paste without touching the slots of the probe. The MPI control unit has a step-by-step test model with the fuel pump relay, separate injectors, idle stabilizing valve, and activated charcoal filter valve, which must have a special fault read-out unit; though one can hear or feel the operation of the parts when the engine is off. In models until 1988, in which the coolant temperature exceeds 20°C (68°F), the wiring plug should be pulled off and an ohmmeter used to measure the contact-to-contact resistance and the result should be about 2400 ohms. To test throttle valve potentiometer, disconnect its wiring plug and with ignition on check voltages between terminals, voltages should be correct; check wiring or potentiometer. At full throttle, the resistance checks on the potentiometer should be within given ranges. In case of throttle valve switch, unscrew the wiring plug and align it to open at a desired feeler blade thickness and screw the screws. The idling switch has a check of resistance that is done with a feeler blade inserted and the resistance of the switch is expected to be infinity and this is checked on an idling switch and should be infinity resistance that should be checked zero and infinity. In the case of air volume sensor, remove the wiring plug and measure voltages at different contacts when the ignition is on, in between the contacts and compare them with the expectancies. In models with coolant temperature senders since 1989, after the engine has cooled, measure the resistance with identified wiring plug disconnected and verify at 20°C (68°F) approximately 2500 ohms and at 80°C (176°F) approximately 330 ohms.