Usually can't tell if it's bad by looking. Recommend you test the sensor using a multimeter. Instructions are pasted below.
OPERATION
See Figure 1
The
Mass Air Flow (MAF) sensor
measures the amount of air which passes
through it. The ECM uses this information to determine the operating
condition of the engine, to control fuel delivery. A large quantity of
air indicates acceleration, while a small quantity indicates
deceleration or idle.
This sensor produces a frequency o
utput
between 32 and 150 hertz. A scan t
ool will display air flow in terms of
grams of air per second (gps), with a range from 3gps to 150 gps.
Fig. Fig. 1: Location of the MAF sensor on a 1991 vehicle
TESTINGSee Figures 2, 3, 4, 5 and 6
-
Visually check the connector, making sure it is connected properly
and all of the terminals are straight, tight and free of corrosion.
-
With the engine running, lightly tap on the MAF sensor and wiggle
the wires at the connector, while watching for a change in idle speed. A
common problem is MAF sensor wire damage.
Fig. Fig. 2: MAF sensor circuit
-
Backprobe using a DVOM set to the Hertz scale between terminals A
and B. Simulate operating conditions by blowing air across the sensor.
There should be a frequency swing from the air crossing the wire in the
sensor. A normal flow signal will be close to 1200 hertz. If the
frequency is not shown, or not proportionate to the air blown across the
sensor, the sensor is faulty.
Fig. Fig. 3: Attach a DVOM to the MAF sensor electrical
connector's top and middle terminals and check for a 5 volt reference
signal
Fig. Fig. 4: Check the middle and bottom connector terminals for 12 volts
Fig. Fig. 5: Connect a DVOM to the MAF sensor and check the air
flow's corresponding voltage reading (0.144 volts in this case) ...
Fig. Fig. 6: ... then use a hair dryer to blow air into the sensor and note the fluctuation in the reading
-
Check for battery positive (B+) volt
age on terminal C and ground
on terminal B. If voltage or ground are not present, check the circuits
back to the PCM for continuity.
-
If you receive the proper amount of voltage at the electrical
connector and still have a driveability problem, replace the MAF sensor.
-
If the sensor and circuits are functional, the PCM may be faulty.
REMOVAL & INSTALLATION
On 1987-91 vehicles, the MAF sensor is the electronics portion
(black) and the aluminum housing to which it is attached. On later
models, the MAF sensor just consists of the electronic portion, mounted
to the throttle body.
1992-99 Vehicles
See Figures 11 and 12
-
Disconnect the negative battery cable.
-
Unplug the MAF sensor electrical connector.
-
Remove the 3 retaining screws, then remove the MAF sensor from the throttle body.
Fig. Fig. 11: On 1992-95 vehicles, the MAF sensor is mounted to the side of the throttle body
Fig. Fig. 12: The MAF sensor is attached to the top of the throttle body on 1996-99 vehicles
To install:
-
Carefully position the MAF sensor to the throttle body, then install the retaining screws.
-
Attach the sensor electrical connector.
-
Connect the negative battery cable.
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