Toy90

I have a 94 with 135K the water pump looks shiney compared to the rest of the engine which leads me to believe the opti isn't original. It could have been replaced a while ago though with this many miles from a previous owner. Recently it started missing under light load and sometimes feels like I lose 50 hp under more throttle and then it comes back again. Is this the high voltage side of the opti system? I don't have a scanner to check codes yet.

Thanks

rsafier

If you aren't getting codes then it very likely is. The high voltage side will not give any codes. You know when your optical side is messed up as you normally will get a Code 16 (low-res) or 36 (high-res) signal failure. I was able to limp around a bit with a Code 36, but would normally die at idle and above 4K, only fix is replace opti completely.

Toy90

So can you just replace the distributor and not the cap and rotor or should you do both? I would like to do the upgrade vented unit where they take a 92-94 unit and hook up vacuum to keep moisture out, but $650 is a little pricey

bogus

the cap/rotor is a pain to replace. Buy the time they are shot, so is the rest of the opti.

The other downside? the labour is the same regardless.

An opti from Chris at Superior Chevy (1.800.728.8267) is about 350.00. Get a new waterpump, too.

Idle stumble and high RPM miss is the death knell of the high voltage side.

NeedSpeed

Didn't they start the sealed opti's in '04?

bogus

no, 1995.

Strick

I have a 92 and replaced the opti as the water pump leaked out the weep hole and killed the opti. If you are going to have it done, it's expensive. I did my own and upgraded a few things while I was in there. I suggest that while you are in there you do the same. I went with a Meziere HD electric water pump, vented a new AC delco opti (via Corvette Clinic's opti vent kit), and replaced plugs and wires. Checkout my Tech Tip under "Meziere coolant pump install" There are better option out there now to replace the OEM opti, as in Dyno-Tech's Dyna-spark.

Toy90

I guess I'm confused as to what comes with the opti. I think it's part number 10457702. I've found them for $350 on ebay, but then I look at Corvette Central and they have a vented unit for $650 that comes with the cap and rotor. Does the one for $350 come as a complete unit with cap and rotor or do I need to buy that seperately? Do I need the cap and rotor at all or just the opti? I guess I should check codes somehow to find out if I have any first. Can you jump any pins to check this or do I need a scanner? I used to do it on my 90, but I don't know if the 94 will do the same?

NeedSpeed

While you can replace the internals, they are generally sold as a sealed unit. Either one, the older or newer should be about $350-$400.

I think I spent about $600 on my Dynaspark. Upgrading to the stock vented isn't trivial as I think the cam pins were a different size. There are some threads about it if you search.

Biting the bullet and going with the Dynaspark I think is worth it in the long run.