HELP! this newbie with his Z-28 please!
Like already asked, does it do it when idling/cold start ups?
Typically the ICM will act up when it's hot. If the mechanic didn't give any care not to protect the opti from getting wet, yes he could have junked it. You can easily bring up a spark plug wiring diagram and TRIPLE check all those are wired and SNUG on the plugs, actually pull them off and listen for the click/pop seal.

