With intermittent issues, you have to test when problem is ongoing. Test when engine is cold, if you haven't.
On cold engine, you could do cylinder compression test on all cylinders, see how # 3 reading relates to other cylinders?
You could spray carb cleaner around intake gasket to see if it effects idle? Anytime you use a flammable spray, there are safety issues. Safety is YOUR responsibility. Keep a fire-extinguisher handy, just incase something unexpected happens.
It very well could be other issue, but, I can't see anything from here.
Wednesday, October 8th, 2014 AT 9:53 AM