[rkreigh]

so we believe we have good DIS, coils, wires, spark plugs, but still no joy?? So within the electrical system likely we don't have a trigger for the coil to fire on the dead hole. This indeed takes a deeper approach to the "root cause" analysis to determine the source of the problem.


It's really hard to help remotely, can you get the car down to VA or up to Chicago?? I'm thinking that either wiring or something maybe in the ECM has gone south but indeed it takes a very methodical approach and testing to trace this type of problem. Parts swapping can be expensive and frustrating even when they are cheap.


Having lots of LT5 trouble shooting experience and spare parts lying around is a big help to pinpoint the problem. This one sounds like a tough one like a bad pin or wiring harness issue. Bet the old coil is fine too. Most times when they go both sides of the coil fail to spark and you lose 2 cyl. I have seen the corrosion on top of the coil towers get really bad too (*mostly on turbo buicks) which causes a weak spark to that cyl.


You've already tackled the "basics" so grab that Factory Service Manual!!! It's also a great help and has some nice trouble shooting trees. You can also reach out to Gordon K. for remote support.




I'd start with Mark H. and see what he advises as next step if you want to work this yourself. Consider compensating him for his remote trouble shooting time as it will save you several handfuls of hair and scuffed knuckles and is the right thing to do.



All else fails, drag it to a pro to get er dun.




Hope to help u!!!