94 chevy s-10 2.2 ltr

Please help! My 94 s-10 would intermittantly not start when the weather began getting colder last fall. 2 weeks ago it failed completely. It turns over, but will not fire. I have no spark. Oddly enough, I went outside with a heat gun and warmed the area around the ignition module after trying to start it and after it was warm to the touch, I got in and it started and ran for a day until I pulled it into the mechanic and from then on, nothing.The crankshaft sensor, coils, ignition module and the computer were all replaced and still no spark. any ideas out there??
Dave H.