stepuptata

Hey guys, I just tore apart one of these opti's to see the inside. There really isn't much there. My question is, what really goes bad is it the cap and rotor button or that little optical sensor. If it is the optical sensor, will the car even start or run. The optical controls the timing, correct? thanks for the advice,troy

Injuneer

I'd say about 75% or more of the failures are for the cap and rotor, maybe 25% or less are the optical sensors. The sensor get plugged up with rust from the cheap carbon steel bearing retainer plate.

If you have a problem with the optical sensor, you get trouble codes - one for loss of the high resolution pulse pattern (engine will still run, but it loses a small amount of timing accuracy), and another for loss of the low resolution pulse pattern (if the low res is lost, the PCM shuts down the fuel pump and injectors, won't run). A lot of the problems with the optical pulse signals can be traced to corroded wire terminals also.

It isn't unusual to find the trouble code for the low res pulse loss when you do a scan. The code will set and be stored if the PCM can't find the pulse signal. I suspect it happens a bit at startup. If its a "stored" code, the engine will still be running. If its an active code, its fatal. The low res pulse tells the PCM which cylinder is approaching TDC so it knows when to fire the injector and the plug. The high res pulse is used to keep track of the cam position as the engine rotates between the low res pulses.

I would have given you the trouble codes, but you didn't mention the year of your car (OBD-I or OBD-II). The 93-94 unvented Opti is physically different internally and externally than the vented 95-97 unit.

Its also possible that the failure can be attributed to a worn bearing, and the unit is frequently damaged following a cam install because the dowel pin on the cam it too long (95-97).

Theres an Optispark Dissection Page that shows the internals of the vented unit.

stepuptata

Thanks for the info. BTW, the car is a 97 with a OBD-1 conversion from PCM for less. Will I still see any codes with the conversion. Thanks.

Steves396lt1

Can you send me pics, and what tools you used to take it apart. Steves396lt1@yahoo.com

mike 96 ws6

Fred, is the optical sensor available from any source in order to replace it without replacing the complete opti?
I don't see much with a search.

1racerdude

Got a new opti complete in the box for sale.

Mtrhds94Z

No.. neither is the'bearing'

Steves396lt1

The bearing is a NPN bearing andis available. Go to the corvetteforum.com C4 section and ask. People have bought and replaced it.

Mtrhds94Z

That would be NTN[the bearing manufacturer] and I did extensive research about 2 yrs ago and it was not available then... [this is for an unvented 93-4 opti]
a search on corvette forum requires membership, and I have no interest in joining...
Maybe since you seem so sure, you can search and post results?[ link to thread, contact info, etc?] I still stand by that it isn't available... and would be very interested in information that denotes/proves otherwise...

Steves396lt1

Here is the part number. There is a US company that sells it, and I will get that tommorow as I am in Guam right now and my hours are off.
SX03A13LUACS25
Have a nice day!

Mtrhds94Z

Thanks, I look forward to a source...
I have as a P/N for the unvented opti bearing # NTN SX0389LLUACS25/L#01..
I believe your p/n is for the vented opti? They are different bearings..

Joebagodonuts

Hey Heres the bearing. I found it on the corvetteforum, dont know which one, and havent seen the other guy that was in Guam, but I wanted to replace my 95's and this is what I got. have to measure to see if its right. But apparently this company can get anything you want. Worth a try. http://forums.corvetteforum.com/show...41&forum_id=48
http://bearingsdirect.com/products/i...d=&prevstart=0