First off, I'm still new at working on a Vette (LT1).
I'm having a few issues with it when it's at operating temperature, kinds think it may be the OptiSpark, my brother (previous owner) had it changed at the Chevy dealer, (expensive) I assume it was changed with a GM unit??? I've seen searching posts on here the MSD units have issues, and some China made junk also, are the GM units the same as came with the car or are they just China junk also? I was also under the impression these are a complete sealed unit, (non-serviceable) searching online, I see you can replace the cap, rotor, completely take apart the distributor. so what goes wrong with these things anyway? Is it really all water related, since mine has not seen rain, or washed under hood or anything like that what else causes failures?
If I buy a new GM OptiSpark unit, is that the best part available today?

Mark

 

when did your brother have it changed at chevy dealer?

if it was 10 or more years ago you are golden as new old stock was still available.

these were ac delco units with mitsubishi optical sensors.


if it was recently, (within past 6 years for sure), i would question what is in there and the quality of it.

about 9 or 10 years ago they (the dealer) started selling these ac delco remanufactured (in china) optispark units.

it might come in the same ac delco box, and sell for top dollar, but it is rebuilt in china. it is not the same quality electronics

they do a good job replacing seals and bearings, but they 'recycle' the optical sensor. which is the heart of the unit. this is the part that goes bad (esp if not a mitsubishi sensor).

all the summit, jegs, cardone, etc optisparks dont have a mitwubishi sensor

you need to do your best to find an oem acdelco optispark - they arent made anymore but you can get occasionally get lucky and find them on ebay if you ask the right questions and dont trust every title you see claiming its an oem one when its not. they also sell for top dollar.

also you need to modify the 92-94 models to add a 95-96 vent harness to make them reliable (search to find out how to do it).

you need to open it up and look for th mitsubishi emblem on the optical sensor.

 

Brother had it changed in 2010, so no telling what is in there. Thanks for the information, I'll be on the lookout for an original one. Just asked my brother, he may still have the original Opti that was replaced, going there later today for a cook out, keeping fingers crossed.

 

Might want to test the icm and coil.

 

agreed. start with the easy stuff first.

dont just throw parts at it, but test the stuff.

that said, dont be surprised if the problem comes back to being the optispark.

in my case (93 with 26k mile), i had load/ stumbles when hot at wot.

the original opti had shrunk/cracked seals (allowing water intrusion) and rust/corrosion inside.

a vent harness would have sucked that out instead of allowng it to sit in there and corrode.

the next point is controversial but its my opinion (others here will disagree):
the other thing that helps is reduce engine op temps.

with reprogrammed fAns and 160 t stat, i dont see ever over 178f coolant temps.

i used to see 220f all the time. they made this engine run hot for emissions purposes.

heat is an enemy of electronics and look where optispark is at

 

I heard back from my brother, appears that in 2010 they only changed the dis cap and rotor, not the whole distributor. So just maybe I still have a Mitsubishi sensor in there. I'm not going to chase parts, just trying to get as much info first as possible. I do have the FSM.
My issues are when 1st startup car runs perfect, when it gets to operating temp it starts to stumble and small pops if accelerating, but always stayed running to get it home, that is until Friday, on the highway at 65mph it just shut off, tach dropped to zero, idiot lights showed "check gauges" pulled over, would fire and start for about 10 seconds and back off, got it home in the garage, pulled the battery and charged it fully, next morning starts up perfect again. My issue always seems to be at operating temperature, (until I was searching for all thing dealing with temp) I didn't know I could check the digital temp only the analog so I don't know what the temp actually was. I do thing I'm going to install a cooler stat and sending unit to turn on the fan at a lower temp, I already have new knock sensors, O2 sensors and EGR valve, waiting to be installed. These 3 items I've read have different operating parameters when the car is cool vs hot. They were not expensive and I wanted to flush coolant anyway.
I'll let you know how it goes, hope to get working on it this week. need to borrow a friends Kwik-lift, to get under it though.

Mark

 

one quick opti test, when it gets hot and shuts down like that, is to observe tach and see if needle still bounces a bit when cranking engine.

i cant remember if the starter is 150 rpm or so, buts it enough to see the tach needle bounce.

my tach would not bounce during cranking, after motor shutoff due to optispark failire under heat.

but when cold, the tach needle would bounce during cranking.

 

My 94 would bog and fart but never died o2s fixed it the torque is 14 lbs on the knocks and just pinch the connectors to remove and pay attention to how the heat shields come off one was a bit confusing. Good time to pull the radiator and give it a good external cleaning as well.

 

The tach would register while cranking, so maybe my Opti is still operational, I'm going to change the O2 and Knock and EGR first anyway.

Mark

 

What do you mean the o2 you have 3 and need to relpace the front two. and two knocks. When removing the knocks turn your head and keep your mouth shut.