Ive got a 94 and ive been plowing through msd optis. Oem broke at 100k-ish miles and was replaced with a full msd kit...wires coil opti and 6al box. Car ran great for 500 miles but one day it started poorly, drove 5 mins and lost all throttle until the engine stalled and never started again. Battery light came on but no CEL. Voltage was ~11.6 and dropped to 10 when cranking but had 0 spark. Opti was under warranty so it was repaired. Reinstalled with a new battery and it was great made it 2k miles before same thing...poor start, loss of power 5 mins later, wouldnt start again, same lights same voltage. This time the ignition coil also exploded. A totally new coil and opti were sent to me, new battery, new water pump, new timing cover gasket and seals...car ran better than it ever had...until the same exact thing happened again 250 miles in. Now im concerned it may not be the opti but something else breaking. Only stock part remaining electrically is the alternator...is it possible the alternator isnt charging the battery enough? I tried using a jump box and dash read 13v then 11.1 when cranking but wouldnt start or even sputter. If that is enough voltage to start what should i look for that may be causing this same issue over and over? Im stuck 250 miles from home in virginia and gotta figure out how to fix this asap

 

MSD optis have been garbage for awhile. The early ones were good. I'd find a stock coil and hit up Petris or see if anyone has a good stock opti with the Mitsubishi sensor. Seeing as your 250 miles from home, makes this a lot tougher. Worse case is a tow out of the question? I once left a car in Vegas for 3 weeks to get fixed wile I flew home.

Can the 6al be on the fritz, anyone know?

 

When I was having an issue a short time ago with my 95 and wanted to see if it was Opti or not IHBD provided the great information below.

Use the onboard diagnostics. You're looking for Module 4, H16. If it is there, clear it, remove jumper, try to start it, recheck codes, if H16 is back, it is the opti. Pretty simple. Takes less than 60 seconds.

EDIT: Generally, if it fires it isn't the opti, because bad opti = no sparks = no sparks, won't fire. "Won't stay running" is something else. Again, what if any codes are in the onboard diagnostics? Both Module 1 and Module 4.

 

Not quite true, bad opti means misfire and runs like crap, gets better as the car gets hot. Runs like crap at next start. Eventually fails entirely and won’t run.

OP, get an opti from a local parts store and get it replaced. Probably a Cardone or other generic, and it will get you home. And might work for several thousand miles.

 

Im stuck in an oreileys parking lot so cant really do the swap. I rented a uhaul and im driving her back to new york tomorrow morning. Never driven a trailer so should be fun for 5 hours once im home ill get to replacing it. Not sure if ill go for my 7th optispark in 2 years or if ill switch to the ls coil on plug kit

 

Never heard of an opti failing in this way. As IHBD said, if the opti sensor fails then the plugs just stop firing altogether. So do the injectors, BTW (they time their firing based on the opti signal). They tend to either run well or not at all. And if they have intermittent failures, they tend to be exactly of what you said: they run fine cold but then stop sensing when they get hot and the car shuts off. There was a great thread somewhere in here where Tom400CFI proved that on video.

Typically, if a starts running badly as the OP described (won't take throttle, maybe runs better when warm than when cold, gets progressively worse until it shuts down completely), the coil is the problem. The fact that one coil literally exploded on him is also an obvious clue. This is easy enough to test: when the car won't run, use a test light to see if the coil is getting an impulse to fire or use a noid light to see if the injectors are getting a signal. If they are, the then opti is fine and it's either the coil or the actual cap/rotor or plug wires. Now, as to why coils keep failing (if that's the problem)? I'm not totally sure, but if they are getting proper voltage then it probably comes down to bad quality coils. If they are getting too high a voltage, then maybe that could hurt them, but the OP already said his voltage is low, if anything.

That's awful advice. Those things are junk and I've seen people who got two in a row that were DOA: you do all the work and the car won't run at all after you've finished. Probably the best option for a new opti now is the Petris replacement. It seems to have a decent optical module. If the OP still has his OE opti, then I would encourage him to consider replacing that.

OP, the whole coil-on-plug conversion thing seems like a huge waste of money and time, and those things also don't always work. The opti system is not nearly as bad as people tend to think, and I bet 90% of the problems that get blamed on them are actually caused by something else (been there, done that). You need to do real diagnostic work to isolate the real problem instead of just making assumptions and throwing parts at it. Here is a decent tutorial that will get you started: How To Test the GM Ignition Control Module (1995-2005). In the process of doing these checks, you'll end up determining if the opti is reading the disc inside and sending a proper signal, as well as checking the ICM and coil functions. Also, unless you're absolutely sure the plugs aren't firing when this failure happens, you should get a fuel pressure gauge and verify adequate fuel pressure.

 

So after changing optis last week i was still waiting on the msd coil so i used the oem. Ran fine. Switched to the msd coil. Ran fine. Now that its dead weve tested both coils and neither are firing. What me, 10 oreileys employees, and 5 msd guys cant figure out is why does changing my distributor fix the problem but the car breaks down the same way each time? I dont believe the msd opti just happened to fail 3 times in a row the exact same way, but a new opti gets the car started first try every time without changing anything else. Besides the ecu and harness nearly every single component of the ingition system has been replaced at one point yet the car still fails the same way each time. Im towing her home today then going on a family vacation for a week but im gonna tear into her at the end of the month. Im worried this may be something wiring related. My ground at the icm harness had 13.5 ohms of resistance and my ground at the opti harness had over 50. I spliced a new temporary ground for the icm and got the ohms down to 0.01. Opti harness grounds to the ecm so didnt want to mess with that yet. I dont have an oscilloscope so cant test the wave signals from the opti but i dont believe the opti is whats failing me. Any other ideas to check would be greatly appreciated

 

Fuel pressure is good. I dont want to go coil on plug as it seems to just open a new can of worms but im so out of ideas as to whats failing me. To add to my list of symptoms on initial startup my idle is high around 900. Did everything to adjust it and nothing worked even after fully warming up. After good long highway miles the idle dropped to 600 or so and ran great. 0 issues. Then after less than 100 more highway miles id get a random bog for 2 seconds and it would return to normal. 5 mins after that the car loses all throttle and revs drop over 5-10 seconds until it stalls. Then it sputters a few times when trying to start. Then the sputters stop and it just cranks with no spark. This exact same thing has happened all 3 times. Temps were all normal and they happened during long highway miles at cruising speeds. No CEL but i do get the battery light as the car dies down to stall

 

You may not need an oscilloscope to test the opti's output. But before trying to test the direct opti output with any kind of tool, just check to see if the injectors are still firing when it fails. That just requires a noid light in line with one injector. Even before that, you should look at the tach when the car starts to falter: does it still appear to register proper RPMs, or does it go crazy or just fall to zero even while the engine is turning? If the latter, that's a real clue that the opti is actually not sending a signal to the engine. But if the tach or injectors still function, then the PCM must be getting a signal from the opti. Also, as mentioned above, if the PCM isn't getting either of the two opti signals (there are low-res and high-res signals), then it should store a code, even if you don't get a CEL. You should definitely scan for codes.

 

All I can say is that's exactly how mine failed. I replaced everything else (plugs, wires, coil, ignition module), checked static and dynamic fuel pressures, checked injectors, and still had a bad misfire when cold, improving when the car got hot (but still not good). I finally dove in and replaced the opti, and it ran perfectly. And yes I used a Cardone replacement and no issues so far, with about 3k miles since I did the job. For the price, it seems to make sense to me. And it takes about 3 hours to replace the optispark, so it's really not a big deal if you do your own work. I'll replace a couple more before I spend the same money as the Petris, and for right now my car is running great.

 

Will scan for codes and check injectors but i do have pressure at the rails. As for the tach it ran fine while the engine ran fine. When the failure happened the tach followed the engine, it dropped from 2.5k to 0 over the course of 10 seconds then the car stalled. When i first tried to restart the car the engine sputtered for 2 seconds and the tach bounced around 300 but it then dropped to 0 and the sputtering stopped. Every restart attempt after theres been 0 sputtering or tach movement

 

i do all my own work and have replaced the opti 4 times so not worried about doing it again. My worry is either 1. something is causing these optis to fail so replacing it with any model wont solve my issue for long or 2. My opti is fine and something else is breaking down each time. The arguement against #1 is what are the odds that 3 optis would all fail within 500 miles and give no codes. Arguement against #2 is if the opti isnt the problem why does replacing it fix the problem in the short term

 

Hmmm. If the tach reached o RPM before the engine actually did (even if the engine wasn't running, was it still spinning as you coasted?), then that does indeed make a case for the opti being at fault. Grab a "noid light" kit from Autozone (you might even be able to borrow a kit on their loaner program) and see if the injectors are getting signals. If they aren't, then it's pretty clear that your opti isn't sending a signal to the PCM. It's not impossible that three optis from Autozone or some other junk importer could go bad. I think I wrote above that a friend of mine got two DOAs from Autozone in a row. The Petris version is the only one currently available that I know of that works well. Another option: go rob any LT-engined car in a junkyard of its opti and either swap the whole thing onto your car or just swap the sensor into your current replacement unit. The OE units had good Mitsubishi sensors. If you can find one in a junk car (any gen-2 V8 should work, so all those trucks and Caprices and such have them), it is likely to still be good.

 

all 3 have been MSD. My oem opti died and it was a long slow death. Bad starts, rough idle, eventually stalled and died after several weeks of poor performance. 2nd opti was an autozone special and it was DOA. Said screw it and got a full msd kid opti coil wires and 6al box. 1st opti blew after 2 months and aprox 250 miles. Msd repaired it. That blew after a month and aprox 1000 miles including 3 days at the tail of the dragon. It handled high temp agressive driving for hours. Msd sent me a brand new opti and that made it a week and 250 miles before dying. Each one has died the same exact way...out of nowhere while cruising on the highway with good temps. I live in NYC so junkyards arent really close. Petris or acdelco get good reviews. Ive also seen people buy the mitsubushi sensor and restore a bad unit. Ill run the noid light test tomorrow and report back. As for the tach it seemed spot on with the engine. The lul hit when i was at 2.5k and the tach fell to 0 as the engine coasted to stall over about 7 seconds or so. Tach seemed to be reading the engine speed correctly as it died. But now during cranking i get nothing.

 

Okay, I can't recall if you should see tach movement with just cranking or not (I no longer have my C4). The noid test will be revealing: if those injectors are still getting firing signals, then the opti is doing its job, and something else is not. I could say the same for the tach, but the noid will be good confirmation, as will the code scan. If you find this to be the case (that the PCM is still receiving a good signal from the opti and sending it to the injectors and tach), then you're going to have to run the diagnostic procedure I linked above to isolate the issue.

You mentioned MSD before, and I forgot. Sorry. The cap and rotor part of their is supposed to be good, but the optical sensor is not. This is the same story with most replacements, and I'm pretty sure that includes AC Delco these days. The Petris unit is the only one I know of now that uses a good sensor. FWIW, my C4 ran the same OE opti for years with many track days in very hot weather and many autocross runs (lots of heat soak) without ever missing a beat. The designs fundamentally work.

 

Ran a ton of tests today. Noid test was a fail no light on any injector. Checked codes and had a dtc 41 code on module 4. Cleared it and ran through the fsm flow chart. Cranked for 15 seconds and it came back. Next i checked terminal B for 1-4VAC and i read 0.2. Next i checked for continuity for between terminal B and the pcm and it was there with 0 ohms of resistance. Fsm says that means faulty pcm/pcm connection. My ecu has been removed and tuned by garrett tuning in summer 2022 and the problems began in fall of 2022. Now im really not sure whats broken...pcm, icm, optispark, or wiring between these units. What more should i check to help narrow this down

 

Okay, so with all that info, the only possible causes could be either a failed opti sensor, a failed PCM (the technically correct term for the ECU in this car), or bad wiring between them. That rules out a lot, so that's good. The DTC is not explicitly an opti code (opti codes are 16 or 36) - it's for a faulty "ignition control circuit - check pigtail harness from distributor for shorts or opens." I'm really not sure how the PCM knows the difference between a bad opti signal (16 or 36) vs a bad wire between the opti sensor and the PCM, but apparently it does. Therefore, my first advice is to check that harness where it plugs into the opti. I wonder if the pins in it are dirty, loose, whatever? Or maybe the weatheproof seal has gone bad and water is getting in? This doesn't 100% rule out the opti IMO, but it makes more sense that when you've replace the distributor you've reset the plug's connection into it, which then seems to go bad after some time goes by. I would also double-check the harness where that signal goes into the PCM, just to make sure. Test for continuity at the pin where it plugs into the opti to the pin where it plugs into the PCM.

I can't rule out your PCM entirely, but it seems very unlikely that a problem would be intermittent and that replacing the opti would seemingly fix it. PCMs tend to either go bad altogether or keep running fine. When they go bad, they tend to run the fans at full speed all the time, or the amplifies inside for the injector circuits (there are two of them) just stop firing the injectors completely (and that doesn't fix itself). So I'm not betting on the PCM, although I'm not ruling it out entirely.

 

Oops, forgot something. Follow the link in my linked diagnostic procedure to verify that a signal is or isn't showing up on terminal B of the ICM. I'm guessing that 0.2v there means there's no signal, but a test light would tell you for sure.

 

im a big music guy as well and pcm is pulse code modulation so i tend to use ecu for everything to not confuse myself but youre 100% correct. As for my connections i measured the resistance of the icm harness and my ground was 13.5ohms. Msd guy said thats high so i made a temp ground and the ohms dropped to 0.01 ohms. Did the same and measured the opti harness ground and it was 50ohms. I was told by msd that the opti grounds to the ecu and there can be circutry increasing the ohms but it seems high. I looked everywhere for the grounds ive been told theyre near the oil filter but i havent had the chance to jack the car up and look under. The main question i have now is since changing the opti has fixed the problem, but clearly something else is at play...is the additional broken component breaking the opti then causing the no start, or is my opti totally fine and will fixing this dtc 41 issue resolve my problem? Could the lack of a tach signal + injector pulse be the result of this dtc 41 error or is it more likely the optical sensor is fried?

 

wow thats an excellent guide. Its genuinely killing me that i have a family vacation and leave at 5am tomorrow. Im gonna be thinking about this car all week lol. Ill perform this test when im back but ill be MIA for a week. If theres any other tests to perform such as ones for the dual connectors on the ignition coil or the opti harness let me know and ill bang em all out when im back. I did test for constant 12v and ground at all the connectors i mentioned but no signal tests