I know most of you will have fixed your saws but I just wanted to add this tip as I haven't seen anyone on the internet mention it;
* Before giving up on your old coil, undo the HT lead from the coil and test the lead. (it is screwed on. With a little effort it will undo in a C-C direction). This goes for almost all coils out there, Saw, Mower, any small petrol/gas motor you might have for your Mill. I've repaired a number of coils because of the build-up of copper oxide/corrosion and only need to replace the HT line. This is available from most Stihl repair shops or eBay. The HT lead must be copper cored with a size of 5mm for a lot of the older Stihl's including the 84 AV.
Hope that helps keep these great saws going a little longer and helps save some money along the way.