'91 Z28 L98 Built. Bought the car nearly three weeks ago and it ran like a champ, not a single flaw except needing some more fine-tuning(car runs rich), but had zero mechanical issues.

Week and'a half ago, I developed a knock and my check engine light starting going off... turned out I lost one of the bolts to my smog pump pulley and it was wobbling. So, I did a smog pulley delete and ran a new belt... solved the knock.

After nearly another week, car was back-firing, loading up, etc. I pulled the plugs and they were fouled, so I put in new plugs. Car ran fine again with little hint of loading up. The loading up bothered me, so I cheated and pulled the plugs and cleaned them(had bit of gas on'em) and wah-lah.

Two days ago the car started missing and I brought it home. Hadn't touched it till last night when I pulled a plug and noticed it was still a little foul. Well, now the car won't even fire... just cranks. It started twice, idled rough and died. This morning, I swapped all the plugs again(had maybe 10 miles on last ones), replaced the distributor cap and the roto bug. Same problem, car acts like it's not getting a spark, just cranks all day.

 

Coil and/or ignition control module. One going bad often takes out the other.

Another possibility, the pick-up coil has gone bad. An even more rare reported failure is the distributor trigger wheel going bad in one way or another.

 

This is what someone else says. Car has MSD... we're afraid it's the Blaster Pak that went bad. Luckily, a buddy has an extra so we're test it all then plug his in and see what happens.