rcssr

I have had this issue for two years now and do NOT want to put another (this would be the fourth one) Opti-spark distributor in this car. It only has 35K miles on it and sits for most of its life. I have a check engine light on and the car shows CODE 36 which I am told is the Opti-spark but it runs fine 99% of the time. I have infrequent stumbles and occasional stall at idle like a traffic light. Chevrolet wants $150.00 to diagnose but I know they will just pull codes as I have done. I have a hard time believing it is that distributor AGAIN (this one has about 2000 miles on it). I have twisted and pulled on the wires and connections at the PCM with no change, runs smooth. I have replaced everything else as well, coil, wires, plugs, etc. Now the guy at Chevy tells me that code 36 is for a number of issues, NOT just the Opti??? Is that true and if so what else? This is the same motor (at least the ignition and Opti) in the 93 Camaro and Firebird. Hopefully someone has an answer for me PLEASE

Cliff Harris

Error code 36 means different things in different years. In your case, see this link for the specific error you are seeing for your year:

https://www.corvetteforum.com/forums...post1576116036

1993C4LT1

If you want, I can post the diagnostic from the FSM.

rcssr

PLEASE do that. I need all the help I can get
THANKS

rcssr

I am happy that you solved your opti-crap issue. Mine is more complex as the car starts and runs fine. I have a check engine light that won't go away and the car shows error code 36 which is that system but it runs. I just don't want the monstrous job unless I am positive. I really feel like pulling the bulb!

antfarmer2

Did you take off or change the icm when you did the coil and not put thermal grease on it?

dizwiz24

i am suspecting the usual problem...

replacement of the optispark with a cheap chinese non-mitsubishi sensor unit. or a more expensive (but also failure prone) msd optispark

and/or not adding a custom late model vent harness to it, while you are in there.

that said, finding an original oem unit is probably difficult but sometimes you get lucky on ebay. gotta ask the right questions (and not believe all the stories).

Mishawaka

DTC - 36 24x Crankshaft position sensor circuit error
DTC - 36 4T60-E Shifting Error
Those are generic codes.
If I recall correctly I think 16 is only code that points towards the opti. At least that's what I remember from my 92 FSM.

I think it also mentioned Low System Voltage but through testing it pointed me to the opti.

Tom400CFI

It's possible for an LT1 to throw a code (even repeatedly) "for the opti", and still start/run. Why? The engine will run on the low res signal only. It knows when each cylinder is at TDC, and therefore that it can fire. The low res signal is generated by the irregularly sized slots on the inside/smaller diameter path of the wheel.



The "Crank signal" is generated by the fine slots on the outer path. The two signals are used together to provide optimal control, but the thing will run on the low res signal only. It WON'T run, the other way around.

Not coincidentally, your code 36 for a '93 LT1 is for "OPTI SPARK IGNITION SYSTEM (HIGH RESOLUTION PULSE)". My guess is that your car is running on only the low res signal.


.

93Rubie

You could test and see if your high resolution and other signals are being produced by the Opti-Spark. That will confirm it bad or good pretty quick.

rcssr

very helpful video BUT since the low resolution wire is blk/red, what color is the high resolution wire (you did not say) I am a pretty good wrench but as far as PCM's and the electronic world, not so much. I need...do this, than that, then this. Since my car runs I presume the low voltage is working. If the high voltage is low or wrong, does that mean bad opti an change it? Is there a plan B?
Thanks, Bob

rcssr

Summit Racing said the vented opti is for a 94 and up and wont work on my 93??

rcssr

Thermal grease used, thanks for the suggestion though

rcssr

FYI: I just put the top down and drove the car 100 miles, half of which in town and half on the interstate at 80MPH. Car was flawless, kicked the crap out of a 5.0 while I was out. The check engine light beamed brightly the whole time though....UGH

Tom400CFI

Since your car runs, it means that at the least, your low resolution signal is working. Since you have a code 36, it's likely that your high res signal is not working (or getting to the ECM). So that is where you need to focus your testing.

dizwiz24

beware. the summit racing optisparks do not have the mitsubishi optical sensor either.

you can add a 95-96 vent harness to a 92-94 optispark by putting on a 95-96 optispark cAp which has provisiona for one of the vent hoses (the air inlet).

you then drill out one of the 3 weep holes to 1/8" and epoxy the other 2 shut) on the base of the unit and use that as the vacuum source.

this is how you retrofit the vents onto a 92-94 optispark.

you can also put on a 95-96 optispark but you need to change camshaft and timing cover. for me, it wasnt a lot of work bc i was putting in a new cam anyways.

you need to find an oem acdelco optispark with mitsubishi optical sensor and add vents to it !!!

look on ebay ! or post here in the parts section that you are looking to buy.

you have to trust me: you are better with a 50000 miles used oem optispark (with mitsubishi sensor) vs. a brand new chinese or msd optispark

rcssr

I have the exact same meter as in the video. I do not know what connector you are referring to "by the intake manifold" please explain in detail (I am not good at this). There is a light blue/black wire and a red/black wire on the same block (one of four) plugged into the ECM mounted at the firewall drivers side. I stripped them back enough to get contact but neither wire gave a reading at all (engine running, ground direct to the battery). I changed the meter to amps (because I have no clue) and got a reading of .20 on the light blue/black wire and .39 on the red/black wire. I stopped at that point for fear of causing damage. Since it runs so well I disconnected the battery to reset the check engine light but it came on nice and bright...UGH
My fear is that I will go through the hassle/expense of replacing the Opti and find it is NOT the problem. My gut tells me otherwise but my brain says 'what can this be?

jsmn4vu

Good decision. Going forward, don't EVER use the amps range until you have schooled yourself on how and when to do it. Basically, it presents nearly a dead short to whatever you connect it to.

To see the high-res pulses, you really need a scope, but you should be able to get a reading using the AC range of your meter.

Good luck!

rcssr

OK I found the mystery connector (4 wire) laying on the intake manifold under the plastic cover on the R/S. Now my issue is that the diagram that is shown above lists the colors totally different than the ones in my car coming from the Opti. I will check the readings on all of them and see where it leads (pardon the pun).

rcssr

Fortunately the connector is marked A,B,C,D so the colors don't mean so much. I used a micro-volt meter to test the leads. I got a reading of 1200 on the A terminal (low resolution) and 110 on the B terminal (high resolution). Do I presume that this means the Opti is kaput or something else? If it were shot wouldn't it read zero? This is way not my world. Now what? Thanks