Testing the Ford mass air flow (MAF) sensor on all of the Ford, Lincoln and Mercury cars and trucks is a very simple test that can be done without a scan tool. All you need is a multimeter. I recommend using a digital multimeter but an analog multimeter can also be used.
Ford has used a Hot-Wire type mass air flow sensor for many years that either comes with or without an internal air temperature sensor. If the MAF sensor has 6 wires, then this is a dead giveaway that it has the air temp sensor integrated inside. If the Ford MAF sensor on your car has 4 wires, then it does not have an air temp sensor integrated within it (the air temp sensor will be somewhere on the air duct that connects the MAF sensor to the throttle body or somewhere on the intake manifold.
On the image viewer on the right, you'll see photos of several different Ford MAF sensors. These come in either a black or light gray body and with 6 or 4 wires in the connector. Regardless of what color body the MAF sensor has or the amount of wires in the connector... they are all tested in the same way!
You can find this tutorial in Spanish here: Cómo Probar el Sensor de Flujo de Aire (Sensor MAF) de Ford (at: easyautodiagnostics.com/es/).
If your Ford or Mercury vehicle uses the MAF sensor in the round Canister Air Filter assembly, go here: Ford MAF in Round Canister Air Filter assembly.
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:
The most common fix I've performed on the majority of MAF sensor problems on Fords have been cleaning it. Now, the symptoms that accompany a dirty (contaminated) Ford MAF sensor are not that harsh or noticeable on engine performance (of course this is not an absolute truth). What I mean is that a dirty MAF sensor doesn't wreak a lot of havoc on the car or truck. Usually the biggest complaints are bad gas mileage and/or a slight lack of power. So how do I diagnose a dirty/contaminated Ford MAF sensor? Well:
Why does it get dirty/contaminated? Well, this MAF sensor easily becomes contaminated with dirt and stuff from the air filter not performing its job or the box that holds the air filter is broken or not sealing correctly. The Ford MAF sensors are some of the easiest MAF sensor to clean. All it takes is to remove the two torx head screws that hold it in place and spray-clean the two hot-wires with a MAF sensor Cleaner.
The second most common problem I have encountered on most Fords (Mercurys and Lincolns) over the years is air leaks between the MAF sensor and the throttle body. It is crucial, yes very critical that you first check that there are no air leaks between these two. 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 (and in the process throwing money away).
How do you check for air leaks? With your eyes and hands. That's right, no special tools required. Just eyeball and physically shake/move the ducting to see if it's loose or disconnected.