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Old 04-18-2016, 02:36 AM   #1
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Default Ignition Problem

I have a 1990 Oldsmobile Delta 88 (Posting this in the Buick section because it seems to be more popular) anyways, the problem I am having is the Ignition Control Module keeps on going out leaving me stranded. I have replaced this part coil pack included 3 times in the last year. On the last replacement I did the Magnavox to Delco system swap. I made sure that the ICM has a nice clean place to ground on the block and the ICM'* continue to fail. I also use plenty of dialectic grease on the mounting plate. I have replaced the plugs and wires with NGK products. The car has always had a slight misfire that is only noticeable at idle even with a new ICM and coil set and I believe that the misfire and ICM failure are related issues. If I run the car for awhile and shut it off for about 20 minutes and start it back up it misfires and shakes for awhile until it warms up then it'* not as bad.

How should I go about dealing with the Constant misfire'* followed by ICM failure?

Any help would be greatly appreciated as I am out of ideas and I don't want to have to say goodbye to such a great car! (other than this issue).

Thanks,
Matt
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Old 04-18-2016, 07:13 AM   #2
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Just because we all own Buicks doesn't mean we don't stop by other sections.

There is two possibilities, either the icm is fine, and something is causing it not to work such as a faulty crank position sensor or pcm, or something is frying it, like possibly an electrical fault, such as wiring or too much AC voltage being dumped in the system. What symptoms do you have when things start to go?
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Old 04-18-2016, 10:50 AM   #3
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First place to start, is find out which cylinder is misfiring......

Worst case scenario, I ever had for a misfire on one of these engines, was a cam lobe.....but since you have basically replaced the secondary ignition, we are talking injectors or compression(possible spring, valve problem, etc.).

But even a misfire, should not take out an ICM, that looks like a separate problem.....usually find the problem to be a bad coil that takes out an ICM.....but you have changed the Magnavox coil/ICM for the new 3 individual coil/ICM setup, and are still losing ICM'*....If the coils are all new, as already suggested, there has to be an electrical spike being generated that takes the ICM out....I can't see the crank sensor doing that......but desperate times call for desperate measures....
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Old 04-18-2016, 01:05 PM   #4
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When the first two icms went out it had very weak spark on two of the cylinders but would still run weakly. When the last one went out the car completly died and had very weak spark on one cylinder the rest had no spark.

What would cause a voltage spike?

Matt
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Old 04-21-2016, 06:27 PM   #5
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When the first two icms went out it had very weak spark on two of the cylinders but would still run weakly.
A little clarity here....when did you switch over to the three coils from the Magnavox coil?

Did you replace the ICM, but reused the Magnavox coil? Or did you immediately replaced the ICM with the 3 coil setup? Were all parts new?
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Old 04-22-2016, 12:08 AM   #6
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Each time the magnavox icm would fail I would always raplece the icm and coil pack tower with brand new parts. Last month when the magnavox unit failed I decided to replace it with a known good delco setup from the junkyard. I also put in a new Ac Delco plug wire set. The car still missfires at idle and seems to be getting worse so I dont think the icm has much longer to go before it is cooked. I dont want to buy any new parts just yet because the car always ends up frying the icm anyways in a short period of time, usualy about a month of short drives and its dead.
I could put in a brand new icm and coil setup and the car would instantly start missfiring at idle and boom its dead in a few weeks. Could the computer or harness that connects the icm and computer cause this?

Thanks for the help, im trying not to lose hope.

Matt

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A little clarity here....when did you switch over to the three coils from the Magnavox coil?

Did you replace the ICM, but reused the Magnavox coil? Or did you immediately replaced the ICM with the 3 coil setup? Were all parts new?
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Old 04-22-2016, 11:54 PM   #7
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Have you checked coil output on each cylinder with a spark tester?

Have you disconnected an injector, one at a time, and noticed which cylinder is misfiring? i.e., if you disconnect an injector and the idle gets worse, that cylinder is firing....if you disconnect, and there is no change, that is a problem cylinder...check all....

Access to a Tech II scan tool would immediately show you which cylinder is misfiring...

Fuel pressure is ok?

Have you checked compression?
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Old 04-23-2016, 01:14 AM   #8
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It'* not often we Buick folks hear how much more popular we are than others!

I wonder what the charge voltage is. Also does it fluctuate a lot?

What condition is the battery in?
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Old 04-23-2016, 01:37 AM   #9
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And again, have you checked the system to make sure there is not an excessive amount of AC voltage? That has also been known to fry ICMs.
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Old 04-23-2016, 01:01 PM   #10
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What would be considered an excessive amount of AC Voltage, and how should I test that?

Thanks Again, im still learning.

Matt

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And again, have you checked the system to make sure there is not an excessive amount of AC voltage? That has also been known to fry ICMs.
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