Diagnose The Optispark - LS1LT1 Forum : LT1, LS1, Camaro, Firebird, Trans Am, Engine Tech Forums

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post #1 of 73 (permalink) Old 09-18-2011, 05:56 PM Thread Starter
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Diagnose The Optispark

Since my car has been acting up here latley I've done a ton of research on how the ignition system works(opti icm coil ect...) I came across this video that ges details on how a opti aka abits works and how
to diagnose it.

It kinda bugs me in a way when ppl assume right off the bat when their car is acting up they blame the opti. Now ,this way with the aod of the video they can follow this simple steps

Check to see if you have a signal from the PCM to the ICM on the white wire. While someone cranks it over, check the white wire to ground for 1-4 volts on the AC scale. If that's there, the problem is between the ICM and the coil.

2 of the wires go from the ICM to the coil. With key ON engine OFF, those 2 wires have 12 volts on them. Find them and be sure they have 12 volts with the key on. One of the other 2 wires left goes to ground. Find it and confirm it goes to ground. The last wire left is the one that carries the control signal. It will test out as I said on the AC scale when someone cranks it with 1 to 4 volts AC. Also measure the resistance of the wires on the opti harness.

If you are getting 1-4 VAC on the white wire it means your opti is sending pulses to the PCM which is sending signals to the ICM to fire. Then your problem is not the PCM or harness. It would be ahead of that which leaves the ICM, coil, and opti.

http://shbox.com/1/95_ign_system_schematic.jpg (Diagram courtesy of Shoebox)

Disconnect the ICM connector. Leave the coil connected. Turn key ON engine OFF. Check for dc voltage at harness terminal "A" to ground and and also "D" to ground. You should get 10v dc or more on both terminals.

If you get no voltage then its the coil or ignition fuse.

If you have good voltage, switch the meter to AC and connect the leads to terminal "B" and ground. Watch the metre while someone cranks the engine. You should see between 1 and 4 VAC. If you don't see the proper ac voltage the problem could be the optispark, the harness to the optispark, the PCM or any of the wiring in between.

Measure the resistance of your coil. If its around 5000 ohms or so its fine. Any higher than 7000 ohms means you should replace it. Measure the resistance of the opti harness and if it seems very high, replace it.

So then if your car passes all the above tests, its the opti.

The following information was found in camaroz28.

Buick Know How: LT1 Optispark (ABITS) Distributor Operation and Diagnostics - YouTube


Last edited by R3DLT1; 09-19-2011 at 05:35 PM.
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post #2 of 73 (permalink) Old 09-18-2011, 09:24 PM
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Yeah, that video has been making the rounds for a while, now. It's one everyone should view.
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post #3 of 73 (permalink) Old 09-18-2011, 09:31 PM
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I agree, very good video. Like stepping back in time.

Moving to sticky.



Yep its slow.

Making the world a warmer place one gallon at a time.
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post #4 of 73 (permalink) Old 09-19-2011, 04:41 PM
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Nice I hadn't seen that yet Thanks!!
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post #5 of 73 (permalink) Old 09-19-2011, 05:45 PM Thread Starter
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Edit for more info

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post #6 of 73 (permalink) Old 09-21-2011, 07:28 AM
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Quote:
Originally Posted by R3DLT1 View Post
2 of the wires go from the ICM to the coil. With key ON engine OFF, those 2 wires have 12 volts on them. Find them and be sure they have 12 volts with the key on.
While those wires go between the coil and ICM, technically power is fed from the coil to the ICM.

Quote:
Originally Posted by R3DLT1 View Post
If you are getting 1-4 VAC on the white wire it means your opti is sending pulses to the PCM which is sending signals to the ICM to fire. Then your problem is not the PCM or harness. It would be ahead of that which leaves the ICM, coil, and opti.

Shouldn't that read behind? It should be noted that the opti would only again be involved if there were cap and rotor issues (problems with distributing the spark).

Quote:
Originally Posted by R3DLT1 View Post
Measure the resistance of your coil. If its around 5000 ohms or so its fine. Any higher than 7000 ohms means you should replace it. Measure the resistance of the opti harness and if it seems very high, replace it.
I'll disagree a little. My stock coil read ~8500 ohms and was fine. Aftemarket coils will generally read lower.

An opti diagnosis write-up has been on shbox.com for a long time. It also gives the values you should see at the end of the opti harness.

I'm not trying to pick apart what you wrote, just trying to avoid any confusion.

[edit] Nevermind, I see you didn't write the original text. It was copied from another poster in 2008 (Gripenfelter) on Camaroz28.com (maybe you should have quoted it or perhaps you meant the preceding information was found on that website?). I guess you won't mind my critique.

Last edited by shoebox; 09-21-2011 at 07:40 AM.
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post #7 of 73 (permalink) Old 09-21-2011, 07:51 AM Thread Starter
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Lol! Its all good.

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post #8 of 73 (permalink) Old 09-30-2011, 12:56 PM
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Shouldn't that read behind? It should be noted that the opti would only again be involved if there were cap and rotor issues (problems with distributing the spark).

Thanks for bringing that up, as I was confused and thought the same thing.

Thanks R3DLT1 for posting that info. Thank you Shoebox for the edit.
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post #9 of 73 (permalink) Old 10-08-2011, 11:37 PM
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Angry

Saw this thread and thought I'd tack my problem on to it. If this is poor forum manners let me know.
just came in from the garage disgusted after trying to start my 95 lt1 camaro No spark at the plug good spark at the coil.Just put an msd optispark on last year when I bought the car. I have less than 2000 miles on it! surfed the net found some old forums talking about loctiteing rotor screws is this still a problem? found other comments saying msd had problems when they first came out but now every thing is good.
Guess I'm pulling it apart tomorrow instead of going to the track.
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post #10 of 73 (permalink) Old 10-09-2011, 09:16 AM
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HRM...another MSD opti problem.

Black over White '95 with Red/Dark Grey interior T/B bypass / LT4 HotCam / 1.6 RR / LT4 Knock Module / .030 over / Fresh rebuild / Rebuilt M6 / Electric water pump / Solomon Tune / Powder coated stock intake/ Wrapped Shorty Headers
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post #11 of 73 (permalink) Old 01-23-2012, 10:35 PM
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I have a ? About my opti. About two months ago when i got the car i replaced the opti water pump plugs and wires coil. The car never gave me a problem untill today after work . I get threw first gear and then it starts to bog bad and staul. So i cost to the side of the road and try to start it,nothing. Then i start pumping the pedal, dont know why but she started from doing this but its fuel injected so idk.the last time it started doin this it was my opti this is why i did all this work. I live in new york and the streets are slushy due to rain and snow. Ooti nightmare i kno. No check engine light so what do you guys think.
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post #12 of 73 (permalink) Old 01-23-2012, 10:41 PM
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Quote:
Originally Posted by Jims97lt1z28 View Post
I have a ? About my opti. About two months ago when i got the car i replaced the opti water pump plugs and wires coil. The car never gave me a problem untill today after work . I get threw first gear and then it starts to bog bad and staul. So i cost to the side of the road and try to start it,nothing. Then i start pumping the pedal, dont know why but she started from doing this but its fuel injected so idk.the last time it started doin this it was my opti this is why i did all this work. I live in new york and the streets are slushy due to rain and snow. Ooti nightmare i kno. No check engine light so what do you guys think.
AC Delco opti?
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post #13 of 73 (permalink) Old 01-23-2012, 10:47 PM
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Yes with a msd cap and rotor.
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post #14 of 73 (permalink) Old 01-23-2012, 10:56 PM
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Quote:
Originally Posted by Jims97lt1z28 View Post
Yes with a msd cap and rotor.
Wait, so did you replace it with a new complete Delco opti a few months back or did you just replace the cap and rotor?
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post #15 of 73 (permalink) Old 01-23-2012, 11:04 PM
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I replaced the distributor and installed a msd cap and rotor a few months back along with waterpump, smogpump,mass air flow, all the o2. Plugs,wires, coil. Alot of money for this too just act up two months later and fuel filter as well. Im kinda upset because i love this car but with school and work, cant be having an opti issue.
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