For the heat treatment to be effective, you will most likely see the ich get worse before it gets better. Don't panic, this is what's supposed to happen.
86 is a good temperature, leave it there. Check your fish daily, and once you see no more signs of ich, leave the temp at 86 for 2 more weeks. Then, slowly bring it back down.
I've successfully used this method a few times with only 1 loss.