LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

did the shoebox opti tests, now what?

Old Sep 12, 2019 | 09:49 PM
  #16  
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Re: did the shoebox opti tests, now what?

Originally Posted by zootzee
Continuity between the green from the ICM to the coil good and also between the pink wires.
Exactly how did you check that? It should read less than 1 Ohm.
Old Sep 13, 2019 | 08:19 AM
  #17  
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Re: did the shoebox opti tests, now what?

Originally Posted by Injuneer
Shoebox's procedure is right out of the factory service manual. The 96 manual (same as 97) logic diagram for the ICM/coil system (Vol 2, Part 1, page 6E-836 to 839, STEP 5 indicates:

1 - Turn the ignition off

2 - Disconnect the ICM connector (are you possibly leaving it connected?)

3 - Turn the ignition on.

4 - Using a DVM, measure the voltage at the harness terminals "A" 10.67 and "D" 0.00 to ground.

Do both terminals measure less than the specified value (Value - 10.0 V)?

If not (you only have a problem on "D"), Go to STEP 6.

STEP 6 - Is there only one terminal below the specified value? If YES, go to step 23

STEP 23

1- Inspect the circuit that was less than 10.0 volts for an open or for a grounded circuit.
Looked I don't see anything that looks out of place
2 - If circuit is open or grounded, repair it.

Was an open or grounded circuit found? If NO go to STEP 24.

STEP 24 - Replace the ignition coil
Testing the coil with the volt meter i get a reading of 8.47 on all terminals, by shoebox that is a good reading

If you are sure you have done all the tests correctly, go to STEP 24. Not sure what other choice you have.But you have to be sure you followed the instructions and measured correctly.
I redid all the testing with your post open I looked again at the wires nothing looks out of place and retested the coil. I made notes in red.
Is it possibly the PCM???
Old Sep 13, 2019 | 08:22 AM
  #18  
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Re: did the shoebox opti tests, now what?

Originally Posted by GaryDoug
Exactly how did you check that? It should read less than 1 Ohm.
I set my volt meter to check continuity and put one end one the green wire of the ICM and the other on the green of the coil wire and the volt meter gave the a sound showing continuity. I did the same on the pink wire on the ICM and coil .
Old Sep 13, 2019 | 09:07 AM
  #19  
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Re: did the shoebox opti tests, now what?

I also tried with connectors to hook up a MSD coil (wasn't the correct one for the car, but I knew it was good), and still no spark.
Old Sep 13, 2019 | 10:37 AM
  #20  
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Re: did the shoebox opti tests, now what?

I assume your "volt meter" is actually a muti-meter, and the 8.47 reading is Kohms, or 8,470 ohms.

On the 97, are the coil connector and the ICM connector on separate branches of the harness, like shown in Shoebox's 1995 harness photo:

http://shbox.com/1/harness7.jpg

In effect, the dark green wire goes up one branch of the harness, curves around, and comes out the other branch. The wiring diagram does not show any splices or other things that could be faulty. You did get two different readings on the harness. In post #1 you indicated " "D" I was around 4-5 volts.". In post # 10 you indicated "green - D No volts". Try Gary's suggestion and (both harness connectors unplugged) measure the ohms between the two ends of the dark green wire. A "continuity check" can show good with a single strand of wire connected. But the wire may be frayed or making intermittent contact. Wiggle the harness while measuring the resistance.
Old Sep 13, 2019 | 10:53 AM
  #21  
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Re: did the shoebox opti tests, now what?

OK
On the pink coil wire I get continuity from The pink coil wire to A (pink ICM) and also to (C black ICM)
On the green coil wire I get continuity to D (green ICM) no continuity to C (black ICM)

Does that sound right?
Old Sep 13, 2019 | 11:59 AM
  #22  
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Re: did the shoebox opti tests, now what?

Originally Posted by Injuneer
I assume your "volt meter" is actually a muti-meter, and the 8.47 reading is Kohms, or 8,470 ohms.

On the 97, are the coil connector and the ICM connector on separate branches of the harness, like shown in Shoebox's 1995 harness photo:

http://shbox.com/1/harness7.jpg

In effect, the dark green wire goes up one branch of the harness, curves around, and comes out the other branch. The wiring diagram does not show any splices or other things that could be faulty. You did get two different readings on the harness. In post #1 you indicated " "D" I was around 4-5 volts.". In post # 10 you indicated "green - D No volts". Try Gary's suggestion and (both harness connectors unplugged) measure the ohms between the two ends of the dark green wire. A "continuity check" can show good with a single strand of wire connected. But the wire may be frayed or making intermittent contact. Wiggle the harness while measuring the resistance.
yes sorry multi-meter,I might not have read it correctly or had the red plugged into the right spot when I posted my original post? I have little experience with a multi-meter. Although I am learning through this.

If I hook up the multi-meter the same way I check the coil to check the ohms, and I have the dial set to 200 (the lowest setting) I get a reading of 00.4. does that make sense?

The green wire does loop right from the coil connector to the ICM connector solid no wear good connection as far as I can tell.
Old Sep 14, 2019 | 05:15 PM
  #23  
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Re: did the shoebox opti tests, now what?

when you check continuity on your meter it should be on the lowest range like 200 then touch the probes together, the reading you get should be the same or very close as the reading on the wires you are checking, no more than .1 - .4 ohm
Old Sep 14, 2019 | 09:55 PM
  #24  
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Re: did the shoebox opti tests, now what?

This is important and why I asked exactly how you did it. Did you unplug the connectors and measure from the pins of the connectors, not the wires? you may have done it like that but we need to make sure you are testing the pins as well. Open circuits happen most often at the terminal connections, not usually in the wires themselves.
Also make sure to do the "wiggle" test as Fred explained.
The reason we are stressing this is because the voltage reading you obtained point to an open connection somewhere.
Old Sep 15, 2019 | 09:58 AM
  #25  
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Re: did the shoebox opti tests, now what?

I think I have some light at the end of this tunnel. I hooked up a sort of jumper wires to the coil directly and I'm getting over 10 volts from each terminal. So yes they're seems to be a problem in the connector that goes into the coil. I need to find some new terminals to put into there. I guess it's not making good contact.
Old Sep 23, 2019 | 07:53 AM
  #26  
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Re: did the shoebox opti tests, now what?


After all the great help that I received I found the issue.

Thanks for the help Injuneer and GaryDoug.
Old Oct 5, 2019 | 01:03 PM
  #27  
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Re: did the shoebox opti tests, now what?

That'll do it!
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