97 Taurus ~120,000 miles, 3.0 vulcan engine.
At idle in gear, the car makes a "buzzing" noise from the front of the car,
sounds like a heat shield slapping around, but I can't see anything
obviously loose. If you take it out of gear or touch the gas pedal, it goes
away. Also, if I put the AC on, the noise changes to a random metallic
clang/tap along with the buzzing, like hitting a wrench against a piece of
metal. Again, only at idle in gear, and it goes away as soon as I hit the
gas a touch. The AC functions fine, IE blows very cold air.
I haven't ruled out the heat shield issue, but the totally different (and
much louder) noise when the AC compressor engages makes me wonder.