PCV NIGHTMARE 

Thank you Ford engineers for your wonderful design of the pcv valve elbow on most taurus'.  Yes my friends, this is a project that will live in infamy and is truly masterpiece.  If you are driving down the road and your ford taurus starts acting like it cant idle or dies at a stoplight (no prior warning at all of course), then you might have a problem with the pcv elbow.  It develops a small hole in it almost invisible to the eye and leaks an incredible amount of air into the intake manifold. A good way to diagnose this is to look at the fuel trims if you have a scan tool that will do this.  They will be way rich in order to compensate for the extra air being admitted into the intake manifold through the leak (+10 or more) and it will affect both banks 1 and 2.  An oxygen sensor code will probably be set as it is picking up too much oxygen as well.  Here is a picture of the offending creature I am expounding upon:

There are probably versions of his hose but they are all pretty much the same look and function.  The company Dorman sells a replacement to this and it works pretty good. 

Lesson here?  Check the pcv elbow if your Taurus is misbehaving.  Some mechanics will spend a ton of money replacing the wrong stuff for something simple like this (by the way, anyone can replace this).  Find your Zen mechanic mindset and avoid the stress of owning a ford taurus.