Mystery Starter Problem Options

[AlphaSigma]

So I am posting on behalf of my dad. We recently purchased a 95gt(2.2L) and it has some starting issues. It starts incredibly sporadically. Some days it will start, other days it won't at all. I am getting good cranking, and spark is the issue here. We have hooked up a gauge to test for spark and when it gets spark it will start. Sometimes we hook up to check for spark and when there is no spark and it won't start. We have replaced the distributor, igniter, plug wire, fuel pump and timing belt. The CEL is throwing code 12 if that helps. We honestly can't figure this out, we took it to a mechanic and he said we needed a new distributor, so we replaced it and it started right away, but now only a few days later its back to the same problem of inconsistent spark. If anyone has ever encountered this or has any ideas it would be awesome!