Subaru Repair: 2002 Outback 3.0L wagon, heat shields, many different things

Question
Hi, I feel my 2002 Outback 3.0L wagon vibrating when it idles in traffic or at a red light.  There is also a low rattling noise at the same time and sometimes goes away briefly if I switch my A/C off.  This all began after I towed a trailer loaded with about 500 lbs of stuff from Michigan to California.  Two dealers checked it and said the engine had now problem on their computer diagnostics.  What else can be wrong? Thank you.

Answer
Anthony,

There a a lot of possibilities did the two dealers verify the vibration?  It's one thing to say "we don't know what is wrong"  and another to say it's acting normal.  

The rattle could also be many different things since it is from Michigan I would suspect the exhaust is rusty and the heat shields are now rattling.

 
Justin

http://allwheeldriveauto.com/