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

LT1 coil. Think its bad. Need confirmation.. Shoebox?

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Old 01-14-2004, 06:35 PM
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LT1 coil. Think its bad. Need confirmation.. Shoebox?

Ok... the car wont start.
Cranks but wont fire.
I pulled the wire and plug out on one of the ports.
I grounded the spark plug against my header and shock tower brace and had a friend try and start the car... There was no spark..
It did spark just once on one occassion but we tried again and again but it wouldnt spark it again.

So i looked up Shoeboxes coil test page.
I un hooked the coil and tested it.
The coil read 5.75 thousand ohms on each connector.
But on my coil 1996, there are only 3 leads while on shoeboxs page it has 4 leads. Im guessing its a pre 1996 fbody...

So what does everyone think..
Bad coil...

Just need confirmation on it before i go buy one.. And does autozone or discount auto or napa have a AC delco or equivalent coil? I dont want a junk one. And i dont have time to order one on line.. thanks
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Old 01-14-2004, 06:44 PM
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Yes, your coil is a later model 3 terminal coil. However, it sounds like yours is ok. My MSD Blaster coil actually measures closer to what yours is. That may be one reason they say the 3 terminal coils are better factory coils.

You may have ICM or opti problems.
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Old 01-14-2004, 06:51 PM
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damn.... how do i check the ICM?

If its not that i guess i'll yank the opti again.. it only has 25 thousand miles on it.

thanks for the quick response shoebox
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Old 01-14-2004, 06:58 PM
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Don't know any tests for the ICM, but some auto parts stores can test them.

You can do some other testing, though.
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Old 01-14-2004, 07:01 PM
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Cant get to an auto parts store though.. Can i bring in the coil with the ICM attached for it to be tested? Or does it have to be in the car?

I read up on the ICM in the searchs..

One said his car wouldnt start at all

And 2 said the car would shut off at around 180 degrees..

I suppose i'll go pick up an ICM tomorrow at the dealership.. i dont want to get a generic one...

So with this info the only think i can think of is

That ICM or the optispark.

Any other possibilities...
Fuel is fine,
No spark.
Coil reads 5.75 k ohms..
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Old 01-14-2004, 07:08 PM
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I think all they need to do is plug into the ICM, so it may be ok for it to still be on the bracket with the coil.
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Old 01-14-2004, 07:14 PM
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Shoebox.. I have found that you can test the icm to a point.. but not really.. if you have the pulsing ground on the green wire going to the coil the ICM is good and if you still have no fire it;s teh coil... usualy when the ICM shorts you get a steady ground on the green wire and it will not fire the coil because of it.


usualy what I do is check for injector pulse and the pulsing ground at the Coil and if they are present I know the optical sensors are ok..

I have found the best way to chek spark is with a grounded test light held near the spark tower of teh coil and seeing how strong and how far it reaches
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Old 01-14-2004, 07:27 PM
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hello i just replaced my icm jason crower at sam taylor 55 dollars the dealership wanted twice that price took 3 days to get here though.
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