Subaru Repair: 99 Subaru Legacy, Subaru running roughly

Question
I have a 99 legacy non turbo. Bh5 series, and lately it has been making a popping noise when exalerating. It sounds a lot like a tractor. I have changed the spark plugs but it still doing it. Any ideas to what else it could be. Thanks for your help.

Answer
Hey Joanne,

There are a lot of possibilities.

You changed the plugs but how about the plug wires and coil.  Also is the check engine light on?  

There a few engine sensors that can cause your described condition as well.  These things are expensive and I wouldn't want you to "throw" parts at it.  The best suggestion I have is look at the plug wires and coil for corrosion and burning or oil at the spark plug end of the wire.  If they look ok have it diagnosed by some one familiar with Subaru local to you.

Justin.

 http://allwheeldriveauto.com/