Car dies while driving

Mazda 323 wagon 1989 200,000 k, s 1.5 ltre front wheel drive. Over last 6-8 months my car has developed a problem where as after driving for a while if I stop at shop etc, once up and running Again will suddenly die, will start again after 1 min or so sometimes will not do again other times will repeat several times. Have replaced coil, checked plugs and leads.
a few things I have noticed that are consistent when this happens is. Temp use to always sit on 1/4 now it is about 1/2 way and dosent cool down, gives no warning when engine dies, dosent use water or oil. Last time died it blu a sizeable hole in rear muffler, any help with this would be gladly accepted.?