1989 Mitsubishi Galant Engine misfiring

When starting from cold, my engine idles for a little while, 5 minutes or when the temp approaches normal, no engine check lite, but then starts to misfire until it dies. Then when I tried to start again it wont. Used a spark tester to test all ignition wires including that from coil to the distributor and there was no spark. I can smell unburnt fuel. I measured the ohms according to the Mitsubishi Galant shop manual like the positive to negative and positive to hi-tension terminals and values are ok. Could it be the power transistor. Before the car will run longer time like days before the misfiring occurs but the problem gradually deteriorated that I have no confidence to take the car to the shop a mile away because it might stall.