how do you tell if the optispark distributor is for the older or newer lt1 with out takeing it off?? the newer one has a vent?.reason i just got a miss on one cylinder, i figure for the worst case sanerio.also how are the wires run,the looms seem to be missing.zip ties the plug wires to other things,

Will only be the cap and rotor at worst if its related to the distributor at all mate, pointless to waste money and through away a good part when you only need a cap and rotor.

Telling the difference is theoretically very simple. There is no such animal as a 94.5, its either a 94 or its a 95. If its a 94, its got the old distributor design, provided it hasnt been upgraded (and why youd bother i dont know)

If you really are going to replace it, use an MSD hevery duty unit.

Mine would run for a few days then die. Finaly I bought a DynaSpark and that was three yrs ago. I don't know if their still in business? the DynaSpark is rebuildable.

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Dont skip the simple stuff first. Alot of people tend to blame the opti right off the bat. Check your wires first for cracks. Start the car in the dark & look for the spark arcing to ground. You mention theres missing wire looms/keepers......this may be where the wire jackets wore through and are arcing to ground. Pull the plugs if you can & look at those too. How many miles on them? Do you know which cylinder is missing?

On another note, the worst case scenario being the opti, the job isnt that hard & its not a huge deal really. What sucked the most was running the wires back in their original locations. That took the longest if I remember correctly.

81c3, youre a bloody good bloke mate, and a smart one too. I agree with you on all counts, and im happy to finally see another person that doesnt blame every single drivability issue dirrectly on the distributor!!

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rarely accused of being "smart"...but thanks dude! On a side note, I keep finding myself reading your posts with the queens english accent!! :tongue: ....

depending on the problems, I always suggest checking the coil wire first.

It can chaffe against the waterpump and then start to ground out. It will act much like a bad opti... but it's not.

The Gen I opti (1992-1994), does it have some issues, mostly due to a lack of proper ventilation.

What happens is that water gets in, it floats around as a mist, causes shorts on the contacts, which leads to carbon tracing. The worse case is if antifreeze gets inside... that is super bad. There is no way to get around that... antifreeze eats oils. It gets inside and seeps into the sealed bearing. That will then eat the grease and the bearing is no longer lubed. The lack of lube then causes the bearing to wear down quicky.

Once the bearing wears, the problem gets really bad - the drive shaft that supports the rotor - and the opti side - starts to wobble.

And that leads to codes.

As stated, this is called an Opti-Spark. The Opti - or optical - side is closer to the engine. It is susceptable to oil leaks from the engine and damage to the driveshaft. You see, the optical side is a disc about 2" round. It has 360 small holes on the outermost edge of the disc, within the middle of the ring are 4 holes of different sizes. The outer holes are for engine timing, the inner holes are for fuel timing.

Once a code starts to occur, it could be for either the Hi-res - High Resolution, or timing - or lo-res - Low Resolution or fuel. H16 and/or H36 for pre-1996 cars, IIRC. I don't remember off hand which is which, but either is bad. The only other thing that can gen that code is a bad ECM or a harness problem. Don't let someone tell you a bad knock or O2 sensor will do it, cause it won't!

The aforementioned bearing failures will cause opti codes, too. What happens is the shaft wobbles, the disc loses contact with reality and the optical sensor can't pick it up anymore.

All that it means is that the engine controller has lost contact with the Opti... for whatever reason... if you get both codes, it could be that the harness is in really bad shape, but if that looks ok (and I have seen some corrode), it is more than likely the opti itself.

Moisture is the biggest enemy of the optispark. If it was my car, and I lived in a high humidity/heavy rain area, I would seriously consider replacing the entire unit. Especially if the miles on the unit are over 60k miles. At that point, in that environment, the opti becomes a ticking time bomb.

The wisest thing to do is to take your time, if you can be without the car, I would remove everything, inspect the old opti, and order parts accordingly. If when you spin the drive shaft, and you hear grinding and it doesn't spin easily, replace the entire component set, otherwise, cap/rotor would be ok.

The reason I am suspect of the earlier version is the lack of positive pressure ventilation. The later units have that. You can, tho, retro-fit a vent kit that will do the same thing, perhaps not as eligantly, tho. The other reason is labour - the Opti is a tough nut to crack, and I don't wanna do it more than I have to.

long term storage is also bad, because the moisture will just sit and rust up things inside...

As an aside, my opti has been in for over 100k miles and hasn't thrown one code. I did replace the high-voltage with the LTCC conversion kit, it allows for the use of 8 LS1 style coils. Works great!!! looks goofy, but it works great. www.bailey-eng.com

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HAHA!! Mate thats not the right accent!!! Send me a PM with your phone number ill be able to give you a call on Christmas day, i have made many many MANY phone calls to Colorado over the past 2 years!! @ 2 cents a minute, the pleasure is all mine too

Same goes for the rest of you blokes, but i wont get round to you all, and make sure you give me a time to call, or you might get an early wake up!!!

guy has a ACCEL upti sparkII for 94 1/2 and up... just wondered where the cutoff was for the older version or do they all fit?? thanks

DO NOT USE ACCEL!!!

Junko-rama. They don't use bearings... oillite bushings. They just don't last all that long.

thanks, wasen`t sure why getting rid of it,now we know,

Yes, dont touch ACCEL. Get an MSD if youre really that keen to replace it.

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The cut off was 1995, there was no change during the 94 model year. 1995 and 96 were activly vented rather than the weep holes found in the 92 - 94 versions.

If you have a 92 - 94 your best bet is the MSD or Dynaspark (if they're still in business. I have a Dynaspark by the way). You can upgrade an early unit for a later one but it imvolves changing the timing chain cover among other parts.

Quote: thank you, guess i don`t need to take anything apart,,

A note on the MSD. The connector won't fit the 92 wiring harness. It's not a big deal, just a 4 wire solder and heat shrink.
This info's not in the MSD instructions unless they changed recently.
I have the wiring diagran/connections if anyone wants them.

this is correct. The 1992 Corvette had a 6 pin (used 5) squared connector.

The pin assignments are the same, tho, A = A, B=B and so on. The last one is a ground shield that 1993 and newer didn't use. The last pin was empty.

Yea, the pin assignments on the 92 are the same but the wire colors are different.



Here's the wire connections:
92 LT1 MSD

black/red(stripe) to brown/yellow - low resolution
purple/white to brown/orange - hi res
yellow to red - 12 volt
black/pink to red/green - ground

The 5th wire in the LT1 harness is a ground/shielding wire. It's not needed on the MSD Opti. It doesn't connect to anything on the GM Opti either, just wraped around the other 4 wires for shielding.

yes, the colours are different.

Early optis don't have the venting hoses, unless they've been modified for them. C4s and F-bodies got the later opti in '95. The big cars (iron head engines) got it in '94.

thanks for the info., just checked for wire (bleed) loose sparks, none found,SO i still have a skip like one cylinder not fireing,it just started to,, has been running great..it hasen`t set, i have been driving it, so now it opens a whole new set of things that can be wrong , dosen`t it,,,it has not given any codes ,is the 94 different being the year they changed things in the engine?

As others have suggested, it doesn't really sound like a problem with the opti-spark. Check the plugs and the wires. I replace my early style opti with a '96. It required a '95 timing chain cover and a new harness. Either that or go with an MSD, NOT AN ACCEL! Ever notice all of the ACCEL stickers on "European sport compacts?