s carter

Hi all the other day while driving the car was running great no miss, no hesitation, no problems at all.

while cruising in 5th gear about 45 MPH the car just went dead No Sputter, No pop just off, check engine lite on No Ignition Dead. So I coasted to the side street cranked for a few cycles, No Start, stuck my ear in fuel tank pump cycled, went to fuel rail pushed test port was holding pressure. So like most of us would say Dam Ignition control Module.
Had the car towed home Confirmed No Spark, So I replaced the ICM and Coil, still no spark.

Ran the FSM flow chart and all seemed to pass.
so what we know
Have Fuel and Pressure
Have Injector Pulse (tested with Noid light)
NO spark.
Has anybody seen the Opti-sparks just cut out and fail like this in the past, For that I think is the next Stop and before going there I want to see if there is another place to look first.

WW7

I was going to buy a friends 94, but while test driving the car it shut off just like yours did, it shut off like someone through a switch and wouldn't start back up..He took it to a dealer and they replaced the opti which corrected the problem....So , to answer your question, yes the opti can make a car do what yours is doing..The only electrical things I have seen that will shut a car down like you mentioned is the ICM , Coil, or the opti. Maybe some of the guys on here more familiar with the LT1s can give more/better information.Good Luck ...WW

don hall

Absolutely! My '93 did same thing.... and no code.
My '92 ran, but started poorly, and a code was displayed.

Many threads on opti choices.....some good, some not so good.

If you are going to perform the wrenching, here is an excellent tutorial: https://www.corvetteforum.com/forums...-pictures.html

s carter

Thanks for the reply's, I just wanted to make sure all bases were covered before doing what could be kind of expensive purchase. Now were to get it, The local parts stores have large selection of choices all the way from a $150 Cardone reman to a $550 MSD racing all I want is the car to go not have to revisit the problem, Who offers a reasonable cost good quality Opti

antfarmer2

I would stay away from the msd unless you want the practice

did you look at the harness?

sac just went to a two year warrenty

don hall

I'm hesitant to recommend a replacement opti due to the varying results members have posted.

My last replacement opti was purchased from SacCityCorvettes....non-vented was $170.
They just increased the warranty from 1 to 2 years.
Installed about 2 years ago with about 2K miles.

The SacCityCorvette opti is distributed by AIP, not manufactured by AIP. I have asked SacCityCorvettes and AIP who makes their opti, and have received no responses.

Petris is about $550 with another $55 for extended warranty. The Petris opti has a vented adaptor for your '93. Most members agree a vented opti should last longer than unvented. Some members have had problems with the Petris, others recommend Petris.

Here is a Petris tutorial on opti diagnosis: http://petrisenterprises.com/optispark-distributor/

pcolt94

I assume you checked the spark at the coil as well.

Have you checked fuse #25 10 amp for the coil. If fuse is open, coil and ICM will not work.
If OK, then:

If you have pulses to the injectors using a noid light then the low resolution pulse from the opti sound OK. The ECM cannot develop injector pulses without that drive from the opti. And you would have code DTC 16 but the MIL lamp might not light.

You need to check the ICM drive pulse from the ECM. That would be the white wire to the ICM pin B. If you need the procedure how to do it and a picture I will furnish it.

If there is no drive from the ECM, then the ECM might be a problem.

Red 91

Check the opti wire harness. Good luck!

TorchTarga94

From what you described, it really sounds like the optispark. It really sucks with these cars sometimes. I think the best opti for a pre-95 is the Petris. I have tried a good majority of them (no MSD) and finally landed on the Petris with good results. It comes with a vent harness like the 95+ cars and has a 5 year warranty for an extra $50.00

Do the paperclip method to see if you have any codes. May have an H16 stored in there. If you do, it is the opti for sure.

2VettesMike

Same here, stopped dead right up the street and I coasted into my garage. Tried the coil no luck, Opti fixed it.

Mike

pcolt94

I'm not saying what the problem is or is not here. You don’t get injector drive or pulses unless the low resolution pulse is present to drive and clock thru pulses in the ECM which is where the injector drive comes from. (I assume he made the measurement properly).

Lot of bad opti's out there as I have pointed the finger there myself many times, but you still need to do some basic checks of voltage. Does the ICM and coil have primary 12 volts and is the ICM being driven by the ECM. These are easy things to do and check.

These are some basic things to do before you rip an opti out. Checking connectors, doing a good visual would be some of the items to do.

pkincy

I have both 93 Y body and 93 F Body. I am embarrassed how many good optis I have taken out thinking that was the problem. There are a number of things that should be tested first. Luckily I have 2 pcms given the 2 cars (same pcm different chip) and also have a spare pcm for a grand total of 3. It or one of the pin outs to the pcm is quite often the problem if the ICM and coil and wires are good.

However if you replace the opti and it turns out to be something else, you now have a good garage stock used opti for the next time something quits on you, so no great loss other than it is a relatively expensive part that takes a while to change out. Also I have never change one without putting in a new water pump also. Why not given you have to pull it also.

Decat

So what are your thoughts on replacing the Opti as a wear item? Don't worry about it unless it becomes a problem? I have 90,000 miles on my '94 C4 now, and I would like to do a tune up, spark plugs, wires, but I was wondering if I should do OptiSpark and Water pump at the same time? Don't mess with it until it is a problem?

TorchTarga94

If you aren't experiencing any problems a simple cap and rotor change should suffice.

pkincy

I suppose I wouldn't change the opti without having a symptom that requires it. For all their bad rep they can be surprisingly robust. However 90,000 miles on a water pump is a leak simply waiting to happen. So if you are going to change the water pump you might as well change the opti. When I was changing OptiPukes in the F Body pretty regularly you couldn't get a cap and rotor. But now that you can, and also that some of the aftermarket Optis aren't perfect even when new, I think a cap and rotor change would work when you replace the water pump. That does necessitate you not only pulling the opti but opening it. But it is easy to take a old piece of wood or a small hammer handle and screw in a Torx screw and Voila! You have a tool to take apart your opti. Someone here likely can remember whether it is a T15 or 20 or whatever that you need to back out the reverse torx screws holding the Opti together. (reverse screw=has a head that looks like the business end of a Torx Driver).

s carter

Hi all thanks for all the input, I am a little em-barest to say that I have not really looked at my car lately. after my last post while doing some testing I lost the injector pulse So I installed a New Opti Car still would not start still no pulse, did some various voltage tests and after talking to some friends all said that a proper scan tool would be invaluable to the mission. So we sent it off to a local garage who works on a lot of Corvettes. he looked at it and said it has the Hi & Low and should go so he had the car the did lots of tests tried a different Opti no start , sent the ECM out for testing and refurbish and testing it had some corrosion but tested good so it was cleaned up and sent back, installed no difference still no start no pulse, he said it's probably the CCM I told lets be real sure of this so he did more tests and wire checks. and again he said lets send the CCM out I told Sorry but the well is dry. So i towed it home Pulled the CCM myself sent out and of course it comes back from testing with clean bill of health. so for the last month or two I have had a large paperweight in the garage waiting for a little spare time and a clear mind go though all things from scratch.

93Rubie

I doubt you or your "mechanic" have done the necessary tests. You guys all kill me, this isn't rocket science, get a voltmeter, get a diagram, figure out how the circuit works, THINK about the problem, do the some tests and you WILL find the issue. It really is that simple.

Do you have spark? Yes or No
You state you have no injection pulse. Well that is a pretty simple circuit to diag. You should have 12V on one side and a pulsing ground on the other. Simple test light can do that.

If you don't have 12V check your fuses/wires,etc....if you don't have the pulse to the injector from the ECM. Is the wiring good? Does the ECM have ALL its power and grounds? Does the ECM have all the required INPUTS to make it fire the injectors?

Electrical testing should be done with a loaded and connected circuit. NO OHM meters!!!

What is wrong with the CCM? Did you have a code? Flashing security light? or was it all just a WAG???

Pcolt has some of the better advice on this thread. I would follow what he is saying. Guessing never works. Incomplete or half done testing is just as bad.

dizwiz24

so many people here think a new chinese optispark will fix a problem.

need an oem acdelco (not remanufactured in china acdelco).

they arent made anymore and hard to find

good luck

Purple92

All of the LT1 Owners know that the Opti-spark was NOT one of GM's better ideas - but fundamentally - the ignition system in the LT1 cars is not all that different from any other electronic ignition system.

The opti gets fed power and ground - and it puts out a low res output and a high res output. If one of those is present ant the other one isn't, the CCM will almost always throw a code. If both the high res and the low res outputs are lost - no CEL, as the CCM doesn't know the engine is cranking over. If you have a digital meter with a fairly high input impedance - you can backprobe the 4 pin opti connector on the pass side of the intake manifold to verify you have some kind of low res and high res outputs from the opti.

PIN A - Low Res
PIN B - High Res
PIN C - Plus Voltage
PIN D - Ground

As pcolt94 said - If you have the PCM telling the injectors to fire you have some kind of low res output from the opti. So - if a noid light flashes, and you seem not to have spark - the next place to look is probably the coil & coil driver. Like the old fashioned ignition system in a 60's car - the coil is a brutally simple piece of equipment - when current flows through it - it creates a magnetic field. when the current stops flowing, that magnetic field collapses, which creates a high voltage spark. So - basically the low voltage side of the ignition system is supposed to switch the electricity to the coil on and off. In the old breaker point cars - when the points opened - current stopped flowing the field collapsed, and a was a spark was created. Now - most ignition coils tend to draw a few amps of current - and there is no way that the electronics in the PCM can handle that kind of current - so they use the coil driver module to actually do the switching, (similar to how a relay works = think of the coil driver module as an electronic relay).

So - if you have a low res pulse - the next thing to look at is what's going on at the ignition coil. Like the old breaker point cars - the pos side of the coil always has power - and the connection to ground is switched. So - you should always have 12 volts at the "B" terminal of the ignition coil. You should have a varying voltage - either 12 V or near 0 volts at the A Connector of the coil when cranking and with everything hooked up. If that's the case - you should be seeing a spark coming off the coil (you can pull the coil side of the high tension lead that goes to the opti off the coil - replace it with a old spark plug wire and see if there is in fact a spark coming off the coil when you crank).

If you don't see a change in voltage on the "A" side of the coil when you crank - it's likely the coil driver module is toast - but to verify backprobe pin "B" of the coil driver module with a high impedance digital meter - and you should see the PCM voltage to it changing as you crank. If that's what you see - you need a coil driver module.

Hope this helps !!!!

s carter

Hopefully this weekend I am going to Finally have the right amount of time to spend on doing all the tests that have been mentioned and are in the FSM, to make sure tests get done by a good meter I have a friend with a fairly new meter with nice Leeds not the beat up meter from 20 years ago I have. we are also Soldering some wires on sewing pins to back probe the plugs, as 1 poster said tests should be done under load. and I agree with him the PO loved to Harpoon wires and I have seen a few holes in the Opti Harness (of course had to be in the Car side of Harness) I did check to see if there was any breaks with a Continuity Test and I did have a Circuit How good? Frayed ? I don't trust the purple wire and I will bypass the ugly spot in the wire I have a feeling I might have some Success. I have fixed some other wire rots spots. in other places.