1984 Nissan 300ZX Check Mass Air Flow Sensor

The mass air flow sensor on a 1984 Nissan 300ZX is of the "hot wire" type. The sensor is used by the computer for engine control purposes. It senses the amount of air volume moving into the intake manifold. The computer maintains the fuel mixture at a constant 14:1 ratio. Air temperature, altitude and relative humidity all play a factor in air volume.

Tools Used: Voltmeter

Check Mass Air Flow Sensor

Check the electrical connector on the mass air flow sensor. Pull the connector off the sensor and check for any bent or corroded terminals. Correct as necessary.

Plug the connector into the air flow sensor and start the engine. If the engine does not start, leave the ignition key on. Use the voltmeter to check for power at the electrical connector on the sensor. As you stand in front of the connector, count from the far left wire and check the fifth wire to the right for battery power. Connect the voltmeter red lead to the fifth wire and the black lead to a good ground. If no voltage is present, check the wiring between the computer and the sensor. If voltage is present, go to the next step.

Check the fourth wire for a ground. Turn the ignition key off and turn the voltmeter to ohms. Leave the black lead on a good ground. Probe the fourth wire from the left with the red lead. It should show continuity. If it does not show continuity, repair the ground. If there is a good ground, replace the air flow sensor.

Check the second wire terminal from the left, which is the sensor signal. Turn the voltmeter to volts. Probe the terminal with the red lead. With the key on and the engine off, the voltage should be between 1.5 and 1.6 volts. With the engine running the voltage should be at idle, 2.5 to 2.9 volts. At 2500 rpm the voltage should be 3.0 to 3.5 volts. If any of these voltages are out of parameter, check the fourth terminal from the left for a good ground. These vehicles have problems with the ground circuit, which causes drivability problems such as rough idle and setting oxygen sensor codes. If the ground is good, replace the sensor.

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