Some of you may recall my troubled beginnings with the dealer I purchased my 93 from. They had issues retreiving the title so I went a month on dealer plates.

That problem is resolved and I officially have plates.

My concern is that after the third attempt to take delivery of the car I was furious because it wouldn't stay running, had no power, and started back firing as soon as it was put in gear.

I refused to take delivery...

The next day they told me that the problem was resolved and the car was ready. When I asked what was the problem, they told me that the detailer had steam cleaned the engine and it got wet. All that had to be done was dry it out...

Until I started reading about the numerous OPTI issues on this forum I was in the dark about the lerking potential problem I may have with mine.

The car runs fine, there is no real issue with the way it runs. Should I be concerned? Could a damaged water logged OPTI dry out in one day? Was this an OPTI issue at all?

From what I have read, once an OPTI is bathed it is likely toast.

 

All of us LTx guys have opti concerns.

Enjoy the car while it is running good. Even with a dry opti we never know how long it is going to last. My car has 23k miles, and is on it's third opti.

 

I learned the hard way about getting water on the optispark. This is one place you don’t want to get wet and steam cleaning or pressure washing the engine is the best way to kill it. In case you don’t know were the opti spark is located it’s on the front of the engine just below the water pump. The 92 and 93’s were unvented so any water that gets in stays in. If you have more than 50K on your auto it might be a good idea to change the cap and rotor anyway. When I replaced mine it had lots of corrosion and pitting and with the new one in, it made a world of difference in the performance. If the dealer got the optispark wet and it still runs, they got lucky. Make a deal with them to replace it. If you can replace it yourself you are looking at $500. To have a shop do it $1200.

 

 

How is the car running now. If it misfires or bogs or has a huntting idle thats in most cases a bad opti. Even misfires at higher rpms at WOT are bad opti symtems. They have already admitted guilt. If its still happening you have a good leg to stand on. Have them put in the vented opti if it must be replaced. The better educated you are on this issue the better chance youll have with the dealer. This problem will throw no codes most of the time.

 

If they cleaned the engine with plain water there is a chance that the opti will dry out even if it got wet. The opti is usually killed when a failing waterpump douses it with coolent because coolent leaves a film on the optical sensor. Plain water will evaporate, coolant won't.

The OEM Opti on a 93 is the unvented Gen1 flavor. If you have to have the opti replaced, go with a Dynaspark. Its more expensive than the OEM but much better quality.

 

whew...

this is what happens...

1) water/coolant get inside the high voltage side and cause carbon tracing as they evaporate. Coolant is worse, cause it has stuff in it.

2) coolant gets in and eats the grease inside the sealed bearings. This kicks up a separate problem - drive shaft wobble. This will cause the dreaded codes because the optical reader is no longer accurate. A film will not effect the opti side, because the light beam has to pass through holes.... literally, a completed circuit.

Steam cleaning will kill an opti for a number of reasons, the water, the heat and whatever cleaning chemicals could do a real number on the internal bearings. Finally, the carbon tracing.

Carbon tracing will cause:

1. Low RPM wandering
2. High RPM miss

A bad opti will result in two codes:

16 - low resolution - this means the fuel timing part can no longer do its job.
36 - high resolution - this means the timing part can no longer do its job.

The opti side is a disc, about 2" in diameter. on the outside rim there are 360 small slices. These are used for timing. Inside that row are 4 holes, each a different size, and those are holes are used to fire the injectors. The computer uses both to figure out where it is.

there are two generations of the opti. As a unit, they are not interchangable. Gen 1 is from 1992-1994. Gen 2, 1995-1997 (fbody). The difference is in bearing size and venting. The Gen 1 made due with just three little holes at the bottom to let water out. not very effective. Gen 2 units have a postive flow system that pumps fresh air through the unit. This does a fairly good job of blowing the crap out. Because of the location of the opti (below and behind the waterpump, on the front timing cover), there is no point in replacing just the cap/rotor. The labour is the same either way... and there is not guarentee that the opti itself will live long enough to get full value from that part cost.

MSD and DynaSpark are both making improved optis. MSD is new, but I suspect it will be fine. Both of these units are positive flow.

If you do a Gen 1 EOM opti, you can add a vent to it, but drilling into the cap and epoxying a fitting. The same goes for the base of the opti case, and opening up the drain holes, and attaching more fittings. Finally, neither OEM unit is great at sealing out the elements. I would highly advise using RTV on the cap/chassis joint to be sure it keeps crap out.

Finally, there are options that do away with the the Optisparks spark side - the high voltage. The DelTeq uses a Cadillac Northstar coil pack and the LTCC, which uses 8 LSx coils.

I hope this resolves some of your questions about the opti.

I would go back to the dealer and have them replace the opti NOW. They ****ed it up when they steam cleaned it. Their people don't know jack...

 

With all due respect (and that's a lot), I believe there's room for a bit of additional clarification on the following points that Andy has made:

Carbon tracks in the cap are most likely to cause high-engine-load misfiring, commonly characterized by either a dead miss or backfiring into the intake and/or exhaust. Basically, what happens is that a carbon track develops across the inner surface of the distributor cap, and it becomes a short circuit either between two contacts in the cap (resulting in spark going to the wrong plug at the wrong time), or between a contact in the cap and engine ground (bleeding off the spark energy to chassis ground rather than to the intended spark plug).

The pulses generated by the low-resolution Optical sensor in the Opti are used as camshaft position sensors. The pulses generated by the high-resolution sensor are used to calculate camshaft velocity and acceleration. The ECM uses both of these inputs (and inputs from numerous other sensors) to determine when to trigger the coil.

The absence of high-res pulses will cripple the ECM's ability to optimally fine-tailor spark timing, but so long as the low-res pulses are present, the ECM will still be able to run the engine with timing accuracy that exceeds that of a conventional distributor (including HEI).

The absence of low-res pulses will completely kill the ECM's ability to determine spark timing, and will cause a no-start/no-run condition, because the ECM will no longer have any indication of camshaft position.

Be well,

SJW

 

SJ -

You are correct. It's just that the addition of moisture - especially coolant - only accellorates carbon tracing.

And yes, the opti is a cam position sensor. I just didn't feel like going into that detail... Call me lazy... after typing all that, I figured enough had been covered...

 

Andy is right about coolant getting into these units, and what happens when it does. The presence of moisture contributes greatly to carbon-tracking in any distributor, and the Opti is no exception.

Andy, I'd never call you lazy. You contribute far too much to this Forum for me to ever think such a thing. I just wanted to clarify what you'd written about the low-res sensor, as it could have been interpreted to mean that the low-res pulses are used by the ECM only to run the fuel system. It seemed worth clarifying that it's also used to provide the most important timing info to tell the ECM how to run the ignition system, too. I know you knew this, but somebody reading your post might not have.

Be well,

SJW

 

Exactly... I missed that detail in this post... the two signals are used by the ECM to keep track of the engine... they are independant readings that are used jointly by the ECM.

And I don't mind being corrected when I miss something. Or am not clear enough!

 

You guy's deffinetly know your stuff. I'm not new to backyard wrenching but this electronics stuff and Corvette's are new to me.

Without ripping the car apart to get to the Opti is there anyway to tell if they replaced it to fix the problem? Is it likely that a car running so bad could resolve itself in one day? A rainy day no less...

Would a GenII exhibit this problem if steam cleaned and then return to normal?

The car tends to run okay. I have noticed some low rev drift but equated it to the fans coming on or the compressor cycling. Today however, I was waiting to turn out onto a busy street and when I layed into the throttle it stalled. Not normal for an automatic... I had the dreaded fear that I too was about to experience a flat bed ride home.

It restarted but it reminded me of the old days when you had to pump the gas pedal to get it running. After about 10 seconds it caught and I was good to go.

To be honest, I had so much trouble with this dealer I wouldn't trust them to replace the Opti. And unfortunately, this was an "as-is" purchase. Proving they screwed it up would take 5 lawyers.

I am sure I can replace it myself when I find the time. I'm just not sure this old back is ready to spend several hours bending over to get at it.

 

It's not easy to see much of the Opti without partial disassembly of some components, but you may be able to see enough of it to gauge whether or not it's been replaced very recently if you use an inspection mirror. You also may be able to see a little bit of it from below. I can see a small amount of my DynaSpark by looking down while standing next to the wheel on the passenger's side, if I look from just the right angle.

If your Gen-2 Opti got a bit of moisture inside of it, the active venting system could very well have drawn it out enough to clear the problem, especially since this wasn't coolant, but mostly plain water.

It's not inconceivable that idle speed drift could be due to a failing Opti, but I'd look elsewhere for such a fault before pointing fingers at the Opti. Look at the Idle Air Controller (IAC), look for vacuum leaks, etc. The throttle body may also need cleaning.

I'd suggest you get a fuel pressure gauge on this car if the stalling problem persists. The way it stalled on you sounds to me to be more likely a fuel delivery fault than an ignition system fault.

Yes, you can change your own Opti, if/when the time comes. It's a PITA the first time, but not really all that difficult. It's just a buncha bolts.

Be well,

SJW

 

SJ is right.

Check the basics, before condeming the opti.

Also, with the stalling, I wonder what the condition is of the fuel filter?

They are cheap, tho a pain in the *** to replace.