Uber, as others mentioned, try cleaning it with Iso. Available at most pharmacies, use the 91%.
Also the oxyclean does seem a good bet. I'd disparaged it's use for some time but no more.
I'm currently working an an estate that was really, REALLY bad. Someone here pointed out that with the oxyclean soak you have a good chance at removing possible oxidation that's inside the stem. The pipe I'm working on now, the oxyclean soak has done an incredible job simply soaking, let alone the follow up cleaning with Iso.