I'm looking at a 1993 Corvette 6 speed. It's a two owner car, the second owner being an old friend of mine. He passed away in January of 2015, and his sister has decided to sell it. It's black on black with a leather interior, and only 17,000 miles. I can get it pretty cheap, but wondered if there were any well know trouble spots with that year. Not planning to autocross it, just a street ride.

I think the optispark is about the main known issue. I'm sure there are others, but that's probably the top of the list. I had a 1991, but they have some different issues that may not apply to the 1993 so I won't get into those.

I've read up on the opti-spark. Looks like a huge PITA to get to. Are reliable replacements available? I know plenty of guys here still run LT-1's, so I would assume there are, although I do not know which to buy.

They make kits that take the “spark” of out of opti spark where then only the optical sensor is used. This prolongs their life. I have a lt1 in my 95 caprice and it hasn’t given me any issues (knocks on wood).

We've had great experience with our LTXs, too, and like Rob, knock on wood!

The only time we had any issues was when I _changed_ out the opti chasing a poor running issue on our 95 9C1. While I used NOS Delco parts, the thing failed within a couple of months of the install. Given the crap that's out there, even from the well-known vendors, I threw the old one back in and it was working fine when we sold the car a couple of years later.

Yes, they ARE a PITA to get to, and to do R&R on them, you'll need some specialized tools. The biggest problem appears to be seepage from the water pump which is driven by a shaft that goes through the opti into the pump. Our '96 SS has a Meziere electric pump which allowed the drive shaft to be removed and the drive holes plugged. Other than some dicey wiring for the pump, I've had no issues with the Meziere pump, but I suggest you get two if you're going to depend on the car.

Our other two LT cars, the 95 Camaro and the 95 SS 'garage queen' have their original pumps and optis.

Not sure if the 93 Vette got the vented opti, since that update didn't happen on the B-body until '95, but it's an easy update.

There are a couple of different mods that use just the optical sensor for the trigger, and run LS-style coil packs, which appear to be a bit more reliable. Still, the weak point here is the optical sensor, so it is still a common failure point. Moving to the coil pack ignition, though, does reduce the amount of high-voltage arcs in the opti housing, which will reduce the ozone there, and make the environment in the housing a lot more hospitable.

Once you've done it a couple of times, you can get the opti off in about a half hour taking your time. I find draining the coolant, and refilling it/burping it when done to be the worst parts of the job.

93 didn't have an vented opti. The 92-93 computers are different than the 94-97 computers, and they suck. They require chips to program (later ones can be flashed), and many are experiencing capacitor failure. Remans are getting harder to find. The 92-93 Y-body belt setup is different and requires a two-sided belt IIRC. C4's use the same crappy front hubs as 4th gen, but for street only driving they are fine. Manual cars got the D44 diff, which is very strong, supposedly good to 500-600 hp. ZF6 trans is a good unit, though rebuild parts are harder to find. Clutches are the same as any other LTx, and the slave is external, unlike an LS.

Some here have had good experiences with LTx cars, but I have not. That might be because I'm a shit mechanic, but I swore off ever owning one again after my last C4. I had rotors explode, rotors fall off, and the optical half stop working. I ran LS coils with an aftermarket setup to drive them, but for a 93 car, the best solution is to swap to an LS computer. No more shitty chip flashing, individual coils, and no optical bullshit to deal with. It is the ideal fix. I think it's also possible to drill the intake to run a regular distributor, but I'm not familiar with the details of that swap.

If you can get it real cheap, then great, but C5 prices are pretty low right now, and a C5 is better in every, single, measurable way. YMMV.

Thanks for the replies. Mojave, I didn't realize you could run the LS coils and computer, but if that would improve reliability, it would be worth investigating. I can probably get it for $9500, and would be the 3rd owner. I don't plan to autocross it, but it could happen. I wonder if it's faster than my my '02 Z-28.

The swap to an LS computer requires some work and cash (need a reluctor wheel mounted somewhere and coil mounts, for instance), but it is doable, and in my opinion, is the best fix for opti bullshit. If your Z28 is stock, the Corvette is definitely faster on the same tires. If you start autocrossing on sticky tires, you will have the same front hub problems as a 4th gen. I ASSume the swap brackets to C5 hubs will work on a C4 with longer bolts (the C4 front uprights are aluminum and thicker than the steel 4th gen uprights), but I don't know if anyone has actually tried it.

Chad basically said it all regarding the 92-93 C4's. Since you're not going to auto-x the car, you should be okay. The Opti-spark is the single major failure point in these Vettes; however, that's with lots of accumulated miles typically 100K+. As long as you don't wash the engine with water (like some waxers did when the opti first came out), you should be okay. The only thing that would make me hesitate on buying the car is the age of the electronics and the need for good electrical skills in chasing down electrical failures (which happen from time to time).

Personally, I like the old LT1's and the 6-speed. It's a fun combination to drive and has enough grunt for some spirited driving. BTW, if you ever need to replace the computer, Zip Corvette can re-flash your original unit which is better than a re-manufactured unit.

Hope this helps!

I drove it yesterday, but haven't bought it yet. The opti has to be bad. It pops back, stumbles under load, misses, etc. I plan to run a compression check on it as well. It pretty much sat from 2007-2015 with an occasional start to bring it up to temp. From the time of my friend's death in 2015, it wasn't even started. I thought at first it was injector issues, but I saw coolant on the cross member under the engine. It is a good negotiating tool, however.

Another common cause of ignition issues is the ignition control module (make sure it has grease for the heat sink). Be warned: tracing down this miss could be a fun, fun adventure, especially with a 92-93 ECU.

Pop the gas cap and take a whiff of Jiff. I'm betting you have crap gas. It'll smell like turpentine if it's gone bad. Sitting for three years, no matter where, that gas is bad.

I've had many more issues with bad/old gas than any mechanical issues causing a car to run bad. They'll frequently start and idle, but put a load on the engine, the fun starts.

The fuel pump and strainer was replaced, and new fuel added. a week or so ago. I noticed a bit of spark knock when I put it under load. I didn't check the smell of the fuel, but if it's been sitting, I suppose the injectors could be at fault. Trust me Mojave, I ain't buying unless the issue is found and corrected. I appreciate the help you guys are giving me.

Look up TorqHead out of Canada. They make a true bolt on optispark ignition delete kit so you can run a LS 0411 PCM and coil packs. You also can retain your LT1 wiring harness. All plug and play. No need to remove the timing cover either.

I have been running their system for over a year now and it has been GREAT. Zero issues with it and makes the car much more reliable. For a 17,000mi car I would invest the money to keep it fun/simple and reliable. I've also helped get their PCM to be E85 capable so all the new PCM's are able to take E85 (after adding a sensor,fuel pump and injectors).

Paul is the owner and a GREAT guy to deal with. Highly recommended.
http://www.torqhead.com/index.html

Do they have a complete plug and play kit for a 92-93 y-body? I don't see one on their site after a quick look.

Smitty, maybe I missed it, but I didn't see the '93 Corvette listed. It looks like a great product. I went back to their site. Under "News", they mention that '92,'93 Corvettes are not yet available.

Dove deeper into the car. A buddy brought his Snap On diagnostic stuff with him. The ECM would not communicate with his equipment. The fuse was good, he was surprised it wouldn't read. We drove the car and it ran as bad as last time. We managed to get a couple of codes by crossing the obd pins. One was H41, the other was H72. Crossing 2 different pins made the check engine light blink one long and 2 short times. According to what we had this indicates "12" which is good. The gas smells horribly stale, and unplugging some of the injectors made no difference in the way it ran at all. The anti-freeze I saw on the cross member seems to be dripping from the t-stat housing. I'm wondering now if the problem is the stale fuel causing the issues. I don't think I'll be buying the car, but could the fuel be the main culprit?

Fuel is the main requirement for fire and bad fuel will make an engine do all kinds of stupid things.

A few years back I bought a low mile SOM Camaro SS. I started it and it ran ok, but I didn't drive it. When I picked it up I found that it didn't actually run under any real load at all. It popped and kicked and banged and generally ran poorly (if at all). I babied it home to Ohio from PA trying to burn all the fuel I could. I stopped and filled it up with fresh gas and it was better, but still not really drivable. Ultimately it took fresh gas and new plugs and wires to get it to run properly.

A friend of mine had a low mile '93 C4 that he put an engine in (long story), and he had a few dead cylinders (some primaries were much cooler than others). He wasn't getting signal to the injectors, ECU replacement fixed it.

After having my 1991 Corvette, I don't know that I'll own another one. Those cars were seriously ahead of their time and the technology was just barely up to doing what they were doing. We didn't have the tiny microprocessors we have these days. And the cars really push the limits of the available technology at the time. There are several computers in there that all talk on a common data bus. And it's really interesting trying to troubleshoot things and track the flow of data between units. It's 10 lbs of crap in a 5 (or even 4.5) pound bag. Neat cars and I love driving them...but I don't think I'd do it again. (though I've always wanted an admiral blue ZR1).

Yeah, tis one would start and idle pretty well when cold. Cold start injector, maybe? Once under load all hell breaks loose. Still pondering my next move.

These Vettes didn't have a cold start injector (1988 was the last year). The ECM controlled the mixture while in open loop and it was fairly rich. Once the system went closed loop, the idle mixture was controlled by the ECM using inputs from the MAP sensor, throttle position sensor, idle control valve, oxygen sensors, and temperature sensors for both the coolant and the air inside the intake.

If the car idles poorly in closed loop, look for a vacuum leak if the mixture is too lean or a faulty idle control valve if the engine hunts for an idle rpm. They usually get gunked up over a period of time from oil mist in the throttle body/intake. You can clean it with carb cleaner if you're careful not to get the spray inside the electrical container.

Hope this helps.

It idles pretty well, but once under load it hardly runs at all. Once up to temp, the idle is not real good either.

I’d still bet the BIG problem is the gas. The crap they force us to buy now is marginal right out of the pump. Give it a week, or two just sitting there, and it’s starting to turn on you.

I’ve quit that pump crap in all but our DDs. Everything but the diesel and race car get VP C9, but we have room for storage, and a VP dealer about 10 miles away. I don’t want to ruin another fuel system!

But I digress......

Imagine the carnage after over 10 years. She took it to a dealer, (OMG!), who found it had no fuel pressure. They replaced the pump and strainer, drained the old fuel, and charged her a little over $1,000. I'm still tempted.

Before you go the dealer route, check your fuel pressure by tapping into the Schrader valve on the fuel rails. Turn on the ignition to energize the fuel pump, but don't start the engine. You should see a fuel pressure reading of 43.5 psi (optimal) or a reading within the range of 38-46 psi. If the fuel pressure is off, it will affect the whole system. If your reading is too low, change the in-line fuel filter (underneath the Vette on the passenger side), and then retest.

If the fuel pump needs replacement, it's an easy job on the '93 Corvette. Remove the fuel filler door, remove the rubber tray gasket, and then remove the fuel sender/fuel pump assembly. I've done my '89 several times over the years. (The last time was because 10% ethanol fuel destroyed the ground wiring connection on the fuel sender. The replacement assembly I got from ZIP Corvette for good for E85 so I won't have that problem again.)

If the fuel pressure is within limits, the next suspect would be the injectors (providing there are no vacuum leaks detected). Try Techron fuel injection cleaner first by adding it to the fuel tank to see if that helps. If not, and you haven't discovered another reason for the hard start/idle, you'll need to remove the injectors and have them cleaned/rebuilt or exchanged for new ones. I like the Fuel Injection Connection for their parts and service.

Hope this gets you going!

3rd Gen really is like 8-bit and 4th Gen 16-bit, but what you're describing sounds like a 32X with the Sega CD attached

The air conditioning was computerized, you could pull error codes out of the AC controls. The AC talked to the ECM, there's a body computer that handles lights, doors and the alarm stuff (and others I believe, this is off the top of my head). And I believe there was one more computer, but I'm drawing a blank on what it was and what it handled. I went through the system wiring diagrams really well when I tried to install a FAST XFI fuel injection computer in mine. I left the ECM running and pulled off the wires for the injectors and sensors and such and then moved the fuel pump relay wire over to the FAST system, etc. So I left the ECM operational enough to run the stuff in the car and moved the wires to the FAST for anything that needed coordinated with the fuel injection. It worked perfectly (besides some tuning issues that turned out to be a leaking intake manifold....dumb mistake on my part). I learned just how sophisticated it was when I got into the middle of that project.

Are say, '84s and '85s like that as well?

I don't know if they are quite as bad. I know things seemed to get more advanced with each model year.

To give you an idea.... I could never figure out why I'd start the car and the AC would take a moment to blow on you. I found (in the service manual) that the car directs the air at the floor when you first start it and blows down there for a second so it wouldn't fog the windshield. We've all climbed in the car and had the blower come on and fog up the glass....this car was setup to prevent that by switching to the floor, turning on the blower, counting to 5 or 10 or whatever and moving it back to the settings you had selected.

The current owner already took it to a dealer. I've all but talked myself out of it. Once the fuel issue is fixed, there may still be an issue with the opti. I simply don't want to buy another project.