93 Opti-spark issue
#1
93 Opti-spark issue
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
#2
Race Director
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
https://www.corvetteforum.com/forums...post1576116036
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antfarmer2 (05-25-2016)
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antfarmer2 (05-25-2016)
#5
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!
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antfarmer2 (05-25-2016)
#6
Did you take off or change the icm when you did the coil and not put thermal grease on it?
#7
Race Director
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
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).
Last edited by dizwiz24; 05-25-2016 at 10:30 PM.
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antfarmer2 (05-25-2016)
#8
Pro
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.
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.
Last edited by Mishawaka; 05-25-2016 at 10:42 PM.
#9
Team Owner
Pro Mechanic
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.
.
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.
.
Last edited by Tom400CFI; 05-25-2016 at 11:37 PM.
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s carter (05-30-2016)
#11
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
Thanks, Bob
#12
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).
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).
#13
#14
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
#15
Team Owner
Pro Mechanic
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.
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s carter (06-01-2016)
#16
Race Director
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
Last edited by dizwiz24; 05-28-2016 at 08:32 PM.
#17
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?
#18
Instructor
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!
#19
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).
#20
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