Dead ignition modules??

[PDESORM]

93 transsport 3.8
Last year I replaced my ignition module (coils and all) with a spare one from my scrap 93 transsport. This spring it appears to be acting up again. I went to 2 different, reputable scrap dealers and put in 3 different modules (coils and all..) and motor turns but wont start. I put back my old one from last year, vehicle starts right up (though rough). Is there a trick I'm missing? Is it possible I found 3 defective modules in a row? The scrap yard dealers were all amazed and couldn't figure it out either.
Phil.

[99MBSport]

Instead of replacing the entire module(since it starts the module is good) change the coils to the dead cylinders. I just had the same problem and I changed one coil pack and I was off to the races. Plugs wires may be in the future too. The 3.8's have a tendency to dry out the wires and cause failures.

[PDESORM]

Good idea! You try everything but don't think of the obvious. I have six coils kicking around so I'm bound to find a good one.
I changed the wires and plugs last week hopping it would help.
Do you know if the 3 coils are the same? They are marked with the cylindre numbers but I assume they are the same.

[99MBSport]

All are the same just numbered so you know what wire goes where. Just paint the coil black and renumber it. Mine was the bottom coil pack. It just unplugs whe you remove the two small screws. Good luck