I ran across this great write-up on the mysterious chirping - See "Related Questions" below for more
The author should get bonus points for creative use of stethoscope!
There is a problem with the emissions system.
If the sensor is bad I believe a check engine code will be stored. But if the distributor is chirping there will not be a code. You will hear a chirping sound like a loose belt coming from the drivers side of the engine near the air intake. The camshaft sensor and it's distributor are under the intake, where the ignition distributor used to be. If it is chirping you should replace it (the dist. the sensor is ok) or have it replaced. The gear that drives it also drives the oil pump. If it fails you loose the oil pump as well and there goes your engine.
Usually a worn or frayed drive belt. Inspect all belts and replace any you find that are worn, cracked, or frayed.
chirping is usually a squeaky belt, depending on if it is a constant thing, or if there are certain actions that cause it. You can have your serpantine belt replaced, any mechanic should know how. but honestly, so long as it is not causing any drivability problems, don't worry about it. If it is inside your engine block, though, then you have problems that you should address immediately.
The 2008 Ford Taurus has a V6 engine.
The 2007 Ford Taurus has a V6 engine.
The 2009 Ford Taurus has a V6 engine.
The 2002 Ford Taurus has a V6 engine.
The 2004 Ford Taurus has a V6 engine.
The 2006 Ford Taurus has a V6 engine.
The 2001 Ford Taurus has a V6 engine.
The 2010 Ford Taurus has a V6 engine.