1994 z28.engine dies,will restart after sitting 10 minutes.No spark at coil wire .ignition module and coil replaced.Would bad optispark unit cause no spark at coil wire,

 

It could be the optispark, but then again it could also be the optispark harness, the PCM, or any wiring in between. I would check all the harnesses and connectors for starters and make sure you have good connections. Poor connections can easily lead to intermitent problems.

 

Troubleshooting guide from Shoebox's site: http://shbox.com/1/4th_gen_tech2.html#opti_test