I agree with Rob Forster, MAPP is an acetylene substitute because it burns with a very hot flame. Try using a propane or butane torch instead.
Another possibility is your flame is set towards the oxidising end of the spectrum (excess oxygen, blue hissing/roaring) but for soldering you want to be neutral or reducing.
Another possibility is your flame is set towards the oxidising end of the spectrum (excess oxygen, blue hissing/roaring) but for soldering you want to be neutral or reducing.