A friend of mine has a 1996 V6 Explorer. It has about 100,000 miles on it.
It is having a weird problem with the mass air flow sensor. Sometimes when
it is driving about 35 mph at light load (just cruising), or idling, the
mass air flow sensor lets out a nasty buzzing sound. The one time I caught
it doing it, it definately was in the tube that holds the mass airflow
sensor, and I put my hand on it, and I could feel it vibrating.
I pulled off the sensor, and it appears to be in good shape (Ie there
wasn't anything obviously bad with it). However, when I shook it, there
was a bit of a rattle to it. I don't have another one to compare with it.
My presumption is that the inner metal tube part has unglued itself or
something like that, and when the right amount of air goes through it, it
hits some sort of natural vibration frequency and gets really, really
annoying. This is an intermittent problem. It can drive for an hour
without doing it, or it can do it within 5 minutes of starting. If it is
doing it, and it is stopped, it will continue to make the noise while
idling, but if the engine is accellerated, it will go away.
There is a problem with the NOx system as well (check engine light, with a
'too much NOx flow' and 'too little NOx flow' errors.
It also seems to be idling rough, and fast idling (about 1000 rpm), but I'm
guessing that is part of the NOx issue. However, it has been known to have
the engine actually die when the Mass Airflow Sensor is being noisy.
Another thing I noticed is that it idled terribly when the mass airflow
sensor was disconnected from the air filter, which seems counter-intuitive.
Perhaps there is a restriction in the intake tubes that it needs or
Any thoughts on the noise? Is there a way to fix it, or should he just
spring for a new mass airflow sensor? The NOx issue I have heard is likely
the differential pressure sensor, but because it is a constant issue it
should be relatively easy for a mechanic in the know to fix it.