Well the MAF sensor does exactly what it says. It converts a voltage reading into a grams per second g/s reading that is an INPUT to the PCM. Now the MAF in an explorer may or may not have an IAT (Intake air temp sensor) integrated into it. Check the intake tube for a sensor about 10 inches from the air box, if there is a sensor there than the IAT is external. If not. Internal in the MAF.
The MAF sensor helps in guiding the PCM in to a closed loop operation (this requires many many other sensors too). The MAF is also used by the PCM to diag if there are any problems with the engine. Kinda like if my rpm is 1500 than my MAF should read 12 g/s and then my SFT should be set to this if my O2S11 is reading this. Kinda an a+b+c=x, but if say there is an intake leak.
Maybe your MAF will be correct, ECT (engine coolant temp) is ok, RPM is ok BUT one of your 02 sensors is calling for full rich all the time. Well that would indicate an intake leak.
This is all alot of typing, but I think that the MAF sensor would not be causing the problem. The noise you are describing sounds like somehting I have encountered on B4000's here in Canada. Check and see if the noise is coming from the IAC valve (the silver one on the top of the intake not sure what Ford calls it)
Cosmo. Mazda TEch
Sunday, January 21st, 2007 AT 4:30 PM