Car is still running, but not as normal. Engine missing at low rpm and high rpm. I would recognize the missed fires if I shift to 2nd gear at speed lower than 20mph, or 3rd gear at lower than 30mph......, and at 6st gear with speed lower than 70mph. Should I clean up the Optispark (do the Optispark repair) or replace it? Replacing is expensive, but do not know if cleaning going to help.

 

if your gonna bother doing all the labour just to 'clean' it up, contact carfan18 and get the parts from him. mucho cheaper.

depending on miles and exposure.... you could have 50 miles on it, and if it gets soaked, its done... if you have 80k, it is done.

 

My Vette just passed 60K, that is why I 'm thinking about cleaning it up. However, if the Optispark unit is not that expensive, I will replace it instead of cleaning. How can I contact carfan18? Do you have his email address or website? Also, how much do you think for a new Optispark?

 

I too have a 93 40th, just bought it, simular problems (hope it's not inherent) I have 100,000 on my car, The car is not really missing but gets a shimmy around 850 rpm, and big shimmy on hard acceleration. Most of the gang have suggested a full blown tune up, injectors clean and flow, and fuel filter.

I have heard the optispark runs $600+ new. I may be wrong, someone on here will know. If you find a deal on a replacement, please let me know. My topic to see the advice on my question was "LT1 pro's, go figure" good stuff. Good Luck :cool:

 

you have 100k??? replace the opti.

carfan18 is a forum member, you can page him... or call him at 1-800-728-8267... his name is Jeff Kopp, and is wholesale parts mgr at Superior Chevy. Gives discounts to forum members.

expect the price to be just above 320 for the opti and about 135 for the waterpump. they are both replaced at the same time... mainly because you have to remove the pump to get to the opti.

also, the harmonic balancer must be removed.

get a copy of the feb 2001 issue of corvette fever. there is a detailed article on how to update the opti with the later vented opti. not hard. also, seal the opti with RTV.

what kills these things is water. water gets into the bearing, which cannot deal with said water, and starts to wear out. after a while the bearing cannot maintain true and misses begin.

inside the opti is an optical pickup. once the optical wheel starts to wobble, all hell breaks loose and the car starts to run bad. you see, the optical part sets timing and has a low resolution signal that fires the fuel injection.

expect about 5 hours to do the work... thats taking your time and using hand tools. I don't recommend air tools. you really don't need them and space is limited.

Another maintenance issue with these cars is the radiator... they collect junk in the intake. you may want to consider removing and cleaning the radiator and hoses... serp belt is a good idea, too.

of note, the 92 and early 93 vettes require a 2 sided serp belt!!!!! some dealers may not know this - Jeff does.

 

If you remove the Optispark for inspection, it is fairly easy to assess it's condition. Remove the cap assy and look inside. Spin the bearing and see if it's rough and wobbly. If the bearing is fair, you can clean it, vent it, seal it and reinstall for another 50K miles. The bearing has a very cheap stamped steel type race and they are not real tight or smooth when new. Shaft & rotor optical alignment is largely determined by the cam's precision splined hole unless the Optispark bearing completely falls apart. Misfire is invariably due to moisture induced carbon tracking that results in high voltage breakdown. Removal and thorough cleaning of the cap and rotor assy with soap will ALWAYS rejuvenate those parts, if the problem was common HV breakdown. Optical control failure is very rare and will cause a dash check engine light and code.

See Optispark modification detail in C4 Tech Tips Section and Corvette Fever. Installing a used, modified Optispark is a much more reliable option than installing an unmodified new one that may leak in 3 years. Some owners have gone thru 4 or 5 new, unmodified ones and keep breaking down, writing checks, whining and changing them like underwear. If you properly seal the Optispark with Permatex, a failed waterpump or rad hose will be a non-issue. Personally, I would not spend time and money for peripheral parts (water pump, intake gaskets, rad hose etc) in an attempt to address an ignition gasket/venting design defect.


[Modified by Rick93Z07, 8:00 AM 11/28/2001]

 

Maybe a dumb question, but why are you assuming your "miss" is related to the Optispark? Have you checked the spark plugs? How about the spark plug wires? :confused: