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Old 11-24-2004, 08:07 PM
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Default "SNAP TESTING FORD MAF SENSORS"

Ran across this article on how to test Ford MAF sensors, I was wondering if it is worthwhile or not:

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....the real concern is a skewed input signal at the root of the fuel map causing the computer to work hard, and often out of its window of control, in order to deliver just decent performance at best. So the real question is; how do you test a MAF?

Testing a MAF like a MAP is out of the technicianís realm of ability since installing the MAF on a flow bench and running the calibration software used by the designer is out of the question. We are relegated to monitoring output voltage versus action-reaction events that we control. Grab your scopes and a nearby Ford MAF equipped car and letís get started. Begin by setting your DSO up for a single shot event, 500 mv/div and 1 OOms/div, trigger set to positive@ 1.3-l 5 volts. Next, gain access to the throttle plate because thatís where youíll be performing the snap-rev. We donít use the accelerator pedal due to cable stretch and carpet interference. Now, practice snapping the throttle so fast as to not cause the engine to rev-up too high. Use both hands. We have found that low voltage peaks are caused by techs that donít make the engine take a deep breath. Monitor your test results on your DSO during this snapping of the throttle. Regardless of the engine size, a minimum of 3.5-3.7 volts should be obtained at the waveform peak. See figure 1.With a few baseline tests recorded, remove the sensor and clean both wires with alcohol and a clean, new Q-tip. Retest and notice any increase in the peak and decrease in the idle voltage reading. A dirty MAF will overshoot the idle and undershoot the snap every time. If you have improved the snap, but have not reached our 3.5-3.7 volts goal, replace the sensor. Most new sensors will reach 4.0 volts. Donít forget to check and replace if needed the MAF pigtail, as a voltage drop here will also cause inaccurate readings... Source
So based on this, is it OK to assume that it's also possible to monitor the MAF voltage output during the "snap test" with a common multimeter by simply backprobing the MAF signal wire? Has anyone done this test before?
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Old 11-24-2004, 09:36 PM
Off Road SHO Off Road SHO is offline
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I don't think you can use a DVOM for the snap test because the readout is not quick enough. I am going to try that though, just so I can see what the voltages are.

Tom
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Old 11-24-2004, 09:37 PM
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It should be possible, if your meter has a peak hold function. No, I haven't tried it yet. It should also be possible to test a MAF on a workbench. Use a shopvac for air flow, a powersupply, and check the manual to see what volts to hook up to which wires. That obviously won't be calibrated, but it would show if the MAF responded to air flow changes.


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