....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 technician’s 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 let’s 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 that’s where you’ll be performing the snap-rev. We don’t 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 don’t 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. Don’t forget to check and replace if needed the MAF pigtail, as a voltage drop here will also cause inaccurate readings...
Source
