Common Symptoms of a BAD Ford MAF Sensor
This is not the most definitive list on the subject, but does cover the majority of symptoms I've seen on these types of Ford Mass Air Flow Sensors:
1) MAF Codes that light up the CHECK ENGINE LIGHT (CEL) on your Instrument Cluster.
P0102 MAF Signal Low Input to PCM.
P0103 MAF Signal High Input to PCM.
P1100 MAF Circuit Intermittent Voltage Input.
P1101 MAF Sensor Circuit Output Voltage low During KOEO Self Test.
MAF Sensor malfunction that DOES NOT light up the CHECK ENGINE LIGHT (CEL).
2) Lean and/or Rich code(s).
3) Fuel Trim code(s).
4) A tremendous lack of power upon acceleration.
5) Black smoke coming from the tail-pipe.
6) BAD gas mileage.
7) Vehicle may idle rough and stall.
What we are dealing with:
Do NOT pull the MAF sensor out to test it. Simply loosen up your clamps and turn your air box up to see the wires.
clean your MAF sensor
It is critical that you first check that there are no air leaks between the throttle body and the MAFS. Air entering after the Mass Air Flow Sensor into the engine will negatively impact fuel injection. And will skew the results of your tests which could result in the replacement of a good MAF
Red= 12V +
Tan/Light Blue= Ground provided by ECM
Blue/Red= MAF Signal
How the process works
Use a Digital Multimeter for all tests where a multimeter is called for.
The MAF Sensor produces an analog Voltage signal. This MAF Signal's DC Voltage is directly related to amount of air the engine is breathing. Therefore, if the engine is breathing in more air at 2500 RPM's that at an idle of 900RPM's the Voltage output will be greater at 2500 RPM's than at idle.
Now, when testing this Voltage signal, the important thing to know is not an actual volts number at a specific RPM, but to look for crazy and extreme fluctuations in the voltage signal that do not correspond to the actual air intake (RPM's) of the engine or no Signal at all. For example: If at Idle the Voltage reading starts to spike up and down without you accelerating the engine or if there's no Signal at all.
Later on, I'll show how you'll use a base Voltage reading at idle from the MAF Sensor that will help you to confirm that the MAF Sensor is bad or not.
Test 1: We need +12V
For the next few steps I suggest using a prob or some sort of piercing metal to test the wires so you dont hurt any terminals or insulation. Below is a picture of how i did this.
Use your DMM and prob the red wire to test for 12V+, ground the black wire of the DMM to the negative battery terminal. If you have 12V (11.7-12.6) there, we are ready to move on. If you do not, then MAF is probably not an issue.
Test 2: We need a common ground to the truck
Obviously, for this circuit to work we need a ground to complete it, so prob the Black/White wire with your negative cable on the DMM. Connect your red cable from the DMM and prob the + battery cable. You should get ~12V or whatever voltage your battery is reading 11.7-12.6 is acceptable. If not then, time to check wiring.
Note: the first two Test were simply power and ground from the truck, nothing to do with ECM. The next to steps check voltage and ground from the ECM.
Test 3: Checking for Ground from the ECM
You will need to turn the ignition on for this test!
Once again connect the Red cable from your DMM to the + battery terminal. Then prob the Tan/Light Blue wire the black cable from the DMM. You should once again see ~12V. If not, ECM or wiring issue.
Test 4: Checking MAF SIGNAL
Crank up the engine and get her to idle.
Once the idle stabilizes, take a look at the Voltage number or numbers your Multimeter is throwing at you. This voltage may fluctuate a little or a lot, and this is OK. Whatever they're doing... this is your base MAF Signal Voltage. Should be fluctuating between .8- 1.1 V
Now, open the throttle (manually) to rev up the engine. As the engine revs up... keep your eyes on the Multimeter's Voltage numbers. The Voltage should increase.
When you let go off of the throttle and the idle comes back down, the Voltage reading should also come down and should hover around the numbers you noticed at the beginning of this test.
Rev up and let the Engine come back down several times. Each time, the Voltage numbers on your multimeter should rise and fall smoothly.
If the MAF Sensor is good, the Voltage numbers on the Multimeter should rise and fall smoothly and without gaps. If the MAF Senosr is BAD, you see one of three things: 1.) you WON'T see a Voltage registered on the Multimeter at all or 2.) the Voltage will stay stuck in one number or 3.) the Voltage numbers will spike up and down crazily even when you're not accelerating the Engine.
**Most credit for this goes to easyautodiagonstics.com, they had a great article on a similar model.