So the other day when I was driving across town my 2004 mazda 3 would have a really low bouncy idle and on occasion it would die.
I replaced the spark plugs and i unplugged each coil pack and drove the car around one by one and none of those affected it. Anyone have the same problem and fixed it themselves.?

 

Ifthe tailpipe gets blackquickly, running rich and seems to be holding back when accelerating, I would say either the MAF sensor, or the Purge Solenoid Valve. Both are fairly common problems. Easy to fix, but not necessarily cheap parts to buy. (+/-$100 ea.)