Toyota Repair: 2007 Toyota Camry, toyota camry xle, 2007 toyota camry xle

Question
I have a 2007 Toyota Camry XLE, V6 with about 70K miles.  It recently began
rough idle and fuel economy has dropped almost 10 mpg.  The idle races up and
down.  The car is out of warranty so I am trying to solve this problem myself.  
Could you please give me some things to check or replace?

Answer
With all of this going on there should be a check engine light on, if this is the case the cause should be diagnosed by connecting a diagnostic scantool.Even if the light is not on now there may be some information stored in the history of the computer.