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7 Posts
Discussion Starter · #1 ·
To whomever may offer me assistance,

I have had my 1989 Buick LeSabre Limited for roughly 4 years now. I do love this car and I enjoy its body as well as the simplicity of the engine. There is one issue I have run across that has stumped me and reputable shop in Minot, ND.

I would like to add that this car comes from Canada. km/h on the dash for the big numbers, celsius on the climate control.

Installing a new ICM.

How hard could it be, takes 10 minutes, right?

Hear me out, please.

I installed a new coil pack on my car 2 years ago, on top of a factory ICM with green goo going on.
I drove my car on the highway for 30 minutes, amazed at how it worked out.
parked it in my driveway where it would stay for many days.
No start, turning the ignition caused what sounds like a nasty backfire.
Might run for half a second the dies in a rage.

During this time I went in on the car.
New timing chain, tensioners, belt, water pump, cam sensor, crank sensor, cam magnet, timing sprocket, harmonic balancer, idle air control, fuel pressure regulator (it was spitting fuel into the vacuum), spark plugs & wires. I did all this myself. Not very "hard" just time consuming.
Still no start!

Now I will admit, after all the work, when I went to hook back up the battery; an ark occurred. It was fast, it looked like it went through the alternator?

Anyways, now my climate control unit is fried, for sure.

I take the car to the shop and have them figure out the no start and climate control.

Turns out I needed an ICM/coil pack to start.
New climate control module; obvious.

Here is the catch, you ready?
Shop tells me ONLY a junkyard ICM/coil will work.
Sounds like an upsell or a lazy trick, right?

So I say "okay" and go on my way.
Sure I am upset, I could easily change the ICM and coil with new part for less money than they charged me....

Skip to present day. I drove this car from North Dakota to North Carolina to Florida!
Still has original AC system retrofitted to r134a and AC works good enough to not die in Panama City, FL summer.

I know the car is not running like it should, so I open up the ICM/coil from the junkyard...
On top of that I broke 3 screws into the odd cylinder side, so only even side is "tight."

Time to get a new icm/coil, right?

I have in my possession 2 sets of brand new ICM/Coil.
AC Delco and Standard Ignition.
Both are of the 14 pin variety, as my car has such a terminal harness installed as per factory.
Naturally my 14 pin harness has 13 actual wires running into it.
Why have a ground on K when the body of the ICM should ground to the engine block via obvious connections?

Maybe the new ICM modules do not have a body ground, maybe they need that 14th pin to show them the way?

Anyways I have tried this and that. Installed an extra wire from the ground underneath to the body of the ICM.

With either new ICM/coil installed the engine does the SAME thing it did when i took it to the shop years ago.

Neighborhood surely thinks i drive a POS that cant start when i tinker with this ICM/coil.

Throw my junkyard ICM/coil on and it fires off right away like the baby I know she is.

Explanations please?
Do I need a K ground wire to run a new magnavox ICM?
Im not trying to switch to the type 2 system.
I am afraid that the conversion would waste my time with the same issue?

This is a daily driver for my family.

Used car prices are insane in this area right now.

I am afraid my junkyard ICM will fail soon, I am having troubles finding my parts in a junkyard around here.

In Panama City, FL they crush cars way to quickly.
In North Dakota they keep them around for a long time, pick and pull heaven.

If you read all of this you are a god among men, thank you.

God Bless You All


46 Posts
There's a good amount of information out there if you do a google search. Apparently that green goo is a sign of imminent failure lurking. Maybe this would put you in the right direction even though it pertains more to the delco ICM Difference between Delco ICM's (D1977a)

I know you said you didn't want to, but seems like swapping over to the delco style ignition was popular as misfires & rough idles were not uncommon with the magnavox system. Perhaps the extra ground may have been an update your car didn't receive. Maybe if you make a connector for that empty cavity and grounding it will make your car run right with the new icm. The swap may be something to consider t if you plan on keeping the car for the foreseeable future. Doesn't seem too difficult. Replacing a Magnavox Ignition with a Later Delco Unit - Reatta Owners Journal

Hope your able to get it fixed. It would be a shame to loose a well cared for classic to a modern cuv. The used car prices are insane everywhere

7 Posts
Discussion Starter · #3 ·
There is plenty of information out there for sure! I have looked into this many hours over the years. I am fully aware of the issues of magnavox, with the green goo, and rough idles. I know the issues are caused by heat making units fail over time, the unit failing and also a bad ground due to the mounting surface not being very clean and potentially corroded.

This is indeed why they had the ability for the 14 pin magnavox to have the K ground wire, but it is supposed to be grounded through the body as well.

I know my junkyard unit is grounded through the body, i know all the 13 wires I have are fine, I have pretty much no issue with my junkyard part other than its going to fail sooner rather than later do to the goo. I did clean up some of that good to prevent it from oozing out the side of the coil with broken off screws.

Im not sure why the new magnavox units would be manufactured to remove the body ground, in a wiring diagram for the ICM unit in my haynes manual is clearly states the ICM body grounds and can wire ground. It is always possible! I will test this theory today.

I have no major issue with upgrading to the new style of 3 coil packs and ICM. I just dont want to do it if the same mysterious problem I have is not fixed causing me to revert to junkyard magnavox.

I know the new ICM has to be getting some kind of electrical connections from the 13 pins because when the car turns it either fires right away and immediate backfires itself to death or it spins a couple times fires once, sputters once or twice and then backfires to death. I should mention I have tried to remove the weather strip from the icm terminal to ensure the wiring harness seats all the way down.

If you unplug the icm terminal all together its nothing but free spins for days.

Its just so strange to me and I have never seen a single mention of this exact problem on a forum or in a youtube video.

Ive seen similar issues, but not the same as mine.
A new ICM will not work.
Junkyards are perfectly working.

The only thing ive seen close to this issue was the terminal not connecting all the way due to the weather stripping and the mounting surface and surround area being dirty.

My surface is shiny clean.

Thank you for your help, I hope I can get a break with trying a K ground.

Super Moderator
885 Posts
Congrats on the improved duty location. Haven't dealt with this, but being a junkyard frequenter, I'm always scouring eBay and car-part.com listings for new-to-me parts (just got a fresher trans for my 06 GXP up in Ohio today). The panhandle may not have much inventory, but Central FL should be fairly well stocked, if you want to drive that way for selection.

7 Posts
Discussion Starter · #5 ·
I rigged up an 18 gauge ground wire to the icm with 0 luck. Same ol same ol.

I suppose I am limited to junkyard parts.
I spoke with someone about a local pick and pull that is pretty good. I'll see if they have any ICM/Coil as well as an original MAF. It is hard to come by an original MAF that isnt reman costing more than an aftermarket unit.

I was also told about an old local "buick whisperer" who used to run the local dealership shop. Apparently he only drives leSabres.

Good find on that transmission for you!

If all else fails I can always call up the shop in Minot, ND and have them send me some junkyard units from the area.

I am still hoping someone on this board has solved this issue before.

Thanks all!

7 Posts
Discussion Starter · #6 · (Edited)
Does anyone know the possibility of a failing ecm causing an issue like this? I would assume if the ecm was a problem the junkyard part would not be working too. From my understanding the crank/cam sensors receive ground and power from the ICM directly then feeds their information signal to the ICM where it is sent to the ECM. Then there is the power line to the ICM. The ground wire from the ECM. All the other wires would be information and control wires from the ECM to the ICM.

So given that the engine fires once and then backfires to death on the new ICMs, maybe after the ECM establishes control of the ICM the engine backfires and dies? Perhaps something is amiss with the ecm to where it is unable to communicate with the new ICM correctly?

Though given that system had all its sensors changed two or so years ago and I have never had a CEL in regards to the ICM or ECM. (Only Knock Sensor and O2 sensor. Replaced the 02 and cleaning the knocks connector and body fixed those issues.) I would say since the junkyard unit operates fine, I drive on it daily, the car always starts right up, it might stumble if the engine is hot but it evens out quickly, the system has functional wires and ground; as well as functional sensors.

I believe the car exhibits decreased power and poor starting while running hot because the ICM is old and on its last leg. This idea is supported by the green goo. As you may assume the issue is a daytime summer issue, the car runs cooler at night. Though the issues only happen when the car idles for to long in the heat, driving naturally cools the system enough to regain stability. Also, the AC adds to the summer strain since its going to increase idle temps.

Also, has anyone heard anything about canadian cars using a different icm than american cars? I have not seen anything to suggest this... But I am grasping straws now.

I would like to add that I may be wrong is describing the engine as "backfiring" then dying. The best way to describe it is a violent death that sends a nasty noise to the intake area.

46 Posts
So trying to understand your issue... in short with the junkyard icm the car runs fine when cold, but is having issues when the engine is warm plus it's got the green-goo of death. The two aftermarket icm's the car has violent mis-fires then stalls.

When you swap out to the different ICM's are you swapping to different coils as well or using the same pack?

Assuming your still using the same coil pack when swapping icms, when you installed the aftermarket icm did you try flipping the coil pack around and wiring it back in? It looks like it could plug in either way idk if that would make a difference. Maybe wires are getting crossed somewhere when you plug it in? I'm just guessing. Could just be something so simple its getting overlooked

I'm trying to think back....my father had an '88 Cutlass Ciera 3.8, but I believe that was the LG3 where as yours is probably the LN3. That had the round AcDelco coils, but I believe it had to be converted over at some point. He had an on-going issue with a check engine light that would randomly come on & off with no stored codes, I think that was one of the things he tried changing to fix it, but nothing seemed to work. The car has been gone about 6 years now, but it did make it to 305,000 miles. The original engine & trans were still running strong, but unfortunately the body was giving out.

7 Posts
Discussion Starter · #8 ·
I refuse to use a new coil with the old ICM or to use the old coil on a new ICM. Replacing the coil on my old factory ICM is how i fried it. That is why I am now using a junkyard factory ICM/Coil.

When that happened the trustworthy shop in ND could not get a new ICM and coil to work with my car. That was 3 years ago.

I wanted to check out my current ICM and i broke off the odd side screws in ICM. So now its only torqued down on even side. Its still working and I did clean up some goo to prevent too much from oozing out of the odd side. It does act up when the car is REALLY hot from idling to long on a HOT Florida summer day.

I tried multiple ICM and coil combos.
Ac Delco ICM with Ac Delco Coil
Ac D ICM with standard coil
Standard ICM with Standard Coil
Standard ICM with Ac D Coil

I am not sure how the wiring could get crossed? Sure the wires do touch each other, it is pretty much impossible to wire it without the covered parts of the wire crossing. The exposed wire terminals dont cross any exposed wiring.

I wired it the same way as the factory does which matches the imstructions.

Yellow long to cylinder 1, branched blue to evens.
The other two wires go by length size, though i still followed instructions and factory wiring.

On the AC Delco unit i did attempt to wire the positive on negative and vice versa, mostly because a dude on youtube had his wires that way. His car worked like that! I assumed it worked because of the waste spark nature. In theory you are simply reversing the flow of spark in the coil. I am sure its not good for longevity, but in theory it should work. All that really matters is that yellow is on the 1 cylinder coil pack.

To be honest i even tried to wire the ac delco in a mirrored way, where yellow is 6. Mostly because I noticed there are actually ICM/Coil where yellow is short wire and the ICM terminals are on the opposite side of the device. It was not possible due to the wire lengths and basically what you would end up with is the pack being flipped to where 6 is 1 but its not possible to mount the coil to the ICM with plug wire 1 being able to reach 1 and if you tried to mount the coil correctly for plug wire to reach 1 the 6 inside wires wont reach.

Honestly it is kind of hard to screw up the wiring unless you just reverse + and - which should still work, though i would not advice it.

Honestly when I look at the terminal wiring to the sensors and ECM it seems to me like the issue os related to the ability of the ECM to control the ICM.

I know my crank/cam are good. I have tested what happens if the crank is unplugged and it wont even fire. Free spins just like if the ICM is unplugged.

I know the ICM is getting power and reading the sensors because the car will fire and first crank at fresh install of the new unit, but then it just stalls. If you keep trying to crank it thats when you get the nasty noises and maybe a quick sputter. Most likely because the engine is getting a bit flooded with gas and the spark is reaching it to ignite but since its not being controlled when it starts its "out of timing." Like not physically on the timing chain and gears, but by the computer controls.

I know my ECM works because it runs with the junkyard Factory ICM part, and for about 2 years had no issues at all. The issues with heat have become more common since moving to Florida.

From my understanding after the engine fires quickly, the ECM establishes control of the ICM; basically using the ICM for control of timing. The ICM only controls itself to start the car, once fired it hands over control of itself to the ECM. Now i know technically the ICM still does its own thing and doesnt always respond in the way the ECM wants it to and thats why when the ICM heats up and starts failing it acts badly and never throws any ECM codes. The only time it should throw a code is if the ICM looses crank/cam sensor data; i believe. At least on these older models.

So since the engine will fire right away but stall, I am guessing it has to be the ECM not gaining control of ICM functions.

I could always try to replace the ECM, but I just have a feeling that could go down a rabbit hole I might wish I never did. Like maybe then the new ICM will work, but maybe the ECM will be dumb about other issues involving all the other devices attached to it?

I have seen no signs of issue with my factory ECM other than it appearing to not connect to aftermarket ICM.

I even tried to put the car into service mode with the new icm to see if it would flash me any codes. Tried to start it like that to with no luck.

Like I said the only codes I ever had were in relation to o2 and knock sensors. I needed a new o2 and the knock needs to be cleaned yearly to have a good ground. Oh yeah, I once had an EGR code so i took apart my egr and cleaned it. Even though they say replace the whole unit when it throws a code, the issue was that carbon build up was preventing one of the three ports of operating correctly. Cleaned it with some electronics cleaner and it was good to go. Did that about a year ago.

7 Posts
Discussion Starter · #10 ·
I wish that was helpful lol
He is able to get a new ICM to work in general. He only had issues with coils at first.

I have found and purchased all the parts I need to do a type 2 swap over brand new, believe it or not.
Amazon had most of the parts including the mounting plate. I had to pick up the plate bolts from ebay. Pack of 10 for the OEM ac delco bolts.

I figure id give the new type 2 system a shot! Even if the new unit does not work I can return the D1977a and the D555 coils. Ill keep the mounting hardware so I can try out junkyard type 2 parts. There are a heck of a lot more type 2s in the junkyard than type 1.

46 Posts
That definitely seems the way to go from what I've been reading. I was amazed you could still find the magnavox ones out there. Here its like anything older than 00's seems almost non-existent. I wish you good luck with everything

7 Posts
Discussion Starter · #12 ·

The new set up is working, and what a smooth idle! Has some extra get up as well.

For anyone attempting to upgrade their system, I will list part #s for what I used.
Fair warning though, the only ICM bolts I could pick up these days are too long and too thick!!! It was such a pain getting them to work, you are far better off getting junkyard adapting parts if at all possible.

ICM # D1977a
Coils # D555
ICM/Coil Mounting Bolts # 10467438
Mounting Plate Adapter # 10469468
Adapter Mounting Bolts # 10474166

You are able to use your lock washers from the magnavox unit with the mounting plate adapter bolts, I was able to get these bolts in a pack of 10 from ebay for $20.
The ICM/Coil bolts I purchased are a new design not meant for the adapter plate and gave me a really hard time! Not to mention they were $6.50 a pop from amazon with only 1 in a bag!!!
The adapting plate was $25 and fits like a glove! Though I will warn you that the metal is actually pretty fragile!!! It does not come with threaded holes and even though the ICM/Coil bolts are tapping bolts, getting them to thread is a mess!

I you attempt to use the ICM/Coil bolts I listed to directly thread the holes of the adapter you will fail. It will eat the metal in such a way that it will never bite. Using a drill to help will only cause the issue to be worse. Using your factory bolts from the magnavox unit will allow you to start the process much better, but be careful! If you dont go down 100% straight you will cause the hole to BREAK. thats right, the raised lip with tear off leaving you with just the thin plate to have 2 or 3 threads. Also, if you torque to hard on the old bolt it will BREAK the bolt head off!

I developed a trick to get the new bolts the work and it is as follows.
Start with a drill and the new bolt, give it a little juice to cut a wide starting holes a couple thread deep, your new bolt will not bite.
Take your old magnavox bolt and a 3/8th wrench and start threading making sure you go straight down, not at an angle, and take your time. Do not give it too much torque, if it starts to stick back it out. Blow the hole and bolt clean of metal shreds. Keep using the old ICM bolt like this until you are not to far from the bottom of the adapter, you do not need to make it 100% through the holes 90% will work. In fact if you try to go all the way through you will most likely brake the lip of the hole. If you do break the bolt head you can bite the threads with your clamping drill tip and back it out. If you do brake your holes lip on the adapter it is not the end of the world, just make sure your new bolt can thread in the little bit of hole left.
After you have the pilot holes complete on all 6 holes you can go ahead and assemble the ICM, seals and coils. Install the adapter plate to your mount, place the assembled ICM/Coil on top of the adapter and grab your new bolts.
YOU WILL NEED WASHERS OF SIMILAR SIZE TO THE ONE PRESENT ON THE NEW ICM BOLT. I used 18 washers, but you can get away with 12.
Start installing the new bolts on the side without the coil towers. You do not use washers for these bolts, you will be able to thread them all the way down without issue. I placed a paper towel underneath the mount to catch the metal shreds so they dont get stuck on the serpentine belt. The pilot holes you made earlier with your old magnavox coil bolts should allow these new bolts to thread easily. I stopped when the washer that came with the bolt hit the coil.
Now take 4-6 washers and add them to a new bolt (do not remove the washers that came with the bolt) and tighten it on the side with the coils plug tower. Stop once it is snug on there, the extra washers will prevent the new bolt from hitting the mounting plate your car had from the factory. Without the washer you will not be able to secure the coil to the mounting adapter on the side of the coil tower. Do the same with for the last 2 bolts on the tower side. Now go ahead and finish tightening the side you started on that did not use the washers.

I would like to add something, the D1977a I received had a lot of "extra" plastic inside the wiring terminal where the harness bolt would fasten to. I had to remove the ring that prevents my wiring harness bolt from being removed from the harness and force it through the plastic. It was not easily done, It was impossible to install the harness to the terminal while the ICM was mounted. I highly suggest you remove the harness bolt from the harness and force it into the terminal bolt hole before you install the ICM. It might want to go in sideways, for some reason, just take it out and keep trying until it threads properly. You might want to do it a couple times to ensure the plastic is broken down enough. The threads themselves are perfect for the bolt, it just had plastic blocking them.

Now I have one question. I did not install the seal strip in the ICM wiring terminal, I read that the new ones are very thick and cause issues with connection. Should I have installed this? I did not think much water will be able to get down in there... I could be wrong? I have read some people just throw it away.
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