Have a 2006 subaru outback 2.5L XT that idles rough pretty much all the time and the rpm gauge fluctuates at stop lights. The car also stalls at low speeds about 1/2 a mile from my house when the engine is cool and seems to not do it as much when the engine is warm. No mechanic can figure out what it is yet. Gas mileage is getting bad, check engine light is on. One mechanic thought it was the fuel injector, then an engine coil (although diagnostic does not point here). Now they think it is a head gasket.