Hi group...

I have a '95 Z28 with an essentially stock LT1 and about 150k on it. Always taken care of and runs strong. However, in recent months when I push it hard at WOT it will occassionally "lurch" and lose power for a second as it missing a cylinderor somehow misfiring. It's especially bad when it's hot or after a longer drive and hard to replicate consistently. If I am trying a fast run, needless to say, this will stop me in my tracks.

I've tried a few things, and I'm wondering if it's the optispark or something ignition-related. Or could it possibly be an injector? I changed the platinum plugs/wires around 100k and haven't had anything like this happen before, so I'm stumped and would rather not pay a dealer exorbinantamounts of cash to diagnose/repair this if I don't have to...

Any suggestions/ideas?

Thanks in advance!
-Rob

PS: If this is an optispark, is it a PIA to change?

 

With that mileage, the Optispark is probably due for a change,but also make sure the wires and plugs are good. If you used the OEM plugs they most likely are still good, but for other types 50 K is probably the limit. The opti is not too hard to change, but make sure the new one is installed correctly or the car won't run. You should also change the water pump at the same time because when they leak, they leak on the opti and kill it.

 

I'd say check the plugs first, they're a lot cheaper than a new opti setup. I know that my cylinder #8 has a slightly leaky ring, so the plug gets a whole bunch of oil/carbon residue on it, so after a little it starts to misfire. At 150K the rings may be getting a bit shady, but I agree with Pete, unfortunately it's probably about time for an opti death...

 

Well, sounds like I'm on the right track at least. Even if it's likely an optispark issue! It was pissing me off in a big way on the way home today, as whenever it would rev beyond about 3500rpm the lurching would start...

Unfortunately, the last time I changed the plugs I ended up having to pay a garage to do it because it's such a pain, and THEY almost had the frickin' thing towed to the dealer because one of the last ones was such a chore. Therefore, part of me is hoping it's the optispark afterall, since I have a feeling it would be easier to pull off on my own...

I hate chasing electrical gremlins!

Thanks for the input... Any other ideas?

-Rob

 

Ya, if it's only above a certain RPM, it probably isn't a bad plug. Have fun with the opti, if you do in fact need a new one, I'd go with the MSD system, it's only 100 bucks more than a GM opti, and apparantly performs better at high RPM.

 

this is a great investment... however i had a problem when i installed the MSD. im not sure what kind of wires you have on right now, but i had 7mm autolites when i changed my opti and the distributor was too powerful for those wires. the wires were arching anywhere near metal. in my own experience i would say that if you go with MSD, you might also be looking at a change of wires as well. i changed my wires without dropping anything but the passenger wheel. you can feel every plug while your engine is cold, just do one at a time and dont get them mixed up. took me and a friend of mine about 3 hours, but its better than spending moneybut good luck with whatever you decide to do... i know its not fun