• Hint: Use a descriptive title for your new message
    If you're looking for help and want to draw people in who can assist you, use a descriptive subject title when posting your message. In other words, "2008 LaCrosse" isn't going to indicate to anybody that you need help. However, "Need help with my 2008 LaCrosse" will. Be as descriptive as you can. Please use common sense... This message can be closed by clicking the X in the top right corner.

92 Lesabre poor acceleration, ICM/Coil issue

OptimistPrime

Buick Newbie
49
8
8
Buick Ownership
Buick
My Lesabre has had an issue for a while now, where after it heats up, it runs like crap. Terrible acceleration, it struggled to get above 40 mph. After testing the MAF. air intake and cat converter, I'm pretty settled on the issue being in the ICM or coil pack. But there's an issue that has me confused. My 92 Lesabre with a series I 3800 seems to have the coils and ICM from a series II. The original coil was supposedly a brick like construction, all one unit. The series II coils are three separate modules. The ICMs are also totally different. I went through the wrecks at the junkyard and found some with the brick like coils, others with the series II coils. I grabbed an ICM off an Olds Delta 88, which had the same style 3800 and what appeared to be the same coils as my car. Then I ordered new coils from the internet. I bolted everything on and the car ran wonderfully... for a couple of days. Now it's back to having crappy acceleration, though not as bad as before. It can get above 40 mph at least, but it's nowhere near as good as the car ran yesterday. Really felt like everything was dialed in. It was a guided missile on the interstate and peppy in town to boot.

So now I'm wondering where I went wrong. I swapped back in the ICM that came with the car. Still has the problem. I'm headed back to the junkyard to get another ICM, but I'll probably have to make due with one from a newer car. I hope these are as interchangeable as they appear. If anyone has insight on what the deal is with some of these series I motors having the later vintage coil packs, I'd love to know. Perhaps there was a recall at some point. I know that the only people to ever turn a wrench on this car before I got it was the dealership.

Did I install the ICM wrong perhaps? I used thermal grease as directed, but I'm not sure if I used enough, or the right kind. No one at the auto part store had ever heard of "thermal grease," but I assumed it's the same thing as thermal paste like you'd use on a CPU. My tube of paste even calls itself thermal grease. So I applied some at each of the copper points on the place where the ICM mounts. I'm wondering if I didn't use enough. Am I to cover the entire bottom of the ICM or just the copper contact points? Is this even the right stuff to be using? Like I said, no one at the part store knew what it was.

If anyone has any guidance they can offer, I'd appreciate it.
 

Homer Jay

Full Member
247
59
28
New York
Buick Ownership
2001 LeSabre
You did not mention if you have replaced your plugs and wires. Old and/or damaged wires could cause the issues you are experiencing.
 

OptimistPrime

Buick Newbie
49
8
8
Buick Ownership
Buick
You did not mention if you have replaced your plugs and wires. Old and/or damaged wires could cause the issues you are experiencing.
It does have new plugs and wires, but I'm considering changing the wires again this weekend. I was examining them just now, and they do look a little worn, especially the wire for #5. The plugs themselves have less than 5k miles on them, and are genuine Delco.
 

2007LucerneCXL

Full Member
2,992
899
113
Illinois
Buick Ownership
2007 Lucerne CXL. and 1995 Lesabre currently, past 1973 Riviera, 1968 Riviera
Wires and plugs, according to Internet folklore, are good for 100K but I had a set of GM originals take a dump at 76k so it's possible those wires are a issue depending on milage and years.

On the thermal paste I've used Dow Corning 340 HEAT SINK, it's a little pricey and not sure if anyone else on the forum has had experience with it, but a little goes a long way. I've used the other Dow automotive products, but you probably won't find them at the box parts store as it's more on the commercial side then consumer.
______________________________
 

OptimistPrime

Buick Newbie
49
8
8
Buick Ownership
Buick
Okay, I've replaced the wires and the car still does the problem. I'm at my wit's end with this. I'm going to splurge on a brand new ICM and if that doesn't fix it, I'm selling the car on Craigslist.

I also found out what the deal was with the two ICM configurations, one was made by Magnevox and the other by Delco. The Delco one was also used in the the series II. They're interchangeable, because the junkyard ICM I bought that worked for a day or so was from a 1997 Delta 88 with a series II.
 

HotZ28

Full Member
7,098
345
83
Buick Ownership
1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU
I can feel your pain! There was a change from the Magnavox coils/ICM to the Delco system around 1991-92 and the Delco system was used on all GM 3.8L cars after that changeover. They can be interchanged, but the mounting brackets may be different between makes/models. What kind/brand of coils did you install?? I have installed some aftermarket coils that fail within one week. What cylinders are misfiring? You may not be able to see that on an OBD1 scanner, but the plugs should tell the story. In the 92-94 models, the ICM did not have a direct ground wire in the terminal and depends on the mount for ground. There is a ground terminal below the ICM mount that connects to the passenger side fender. Is that all clean & tight?
 

OptimistPrime

Buick Newbie
49
8
8
Buick Ownership
Buick
They were just no name coils. They're probably not great since they aren't even numbered. I got a label maker and numbered them myself. Hopefully they aren't going bad too. The ground wire is intact. Luckily this car doesn't have much corrosion under the hood. I'm wondering if I didn't apply enough paste and had the salvage ICM cook off when I was sitting in traffic. Bumper to bumper traffic in 90+ degree weather is a nightmare for a car, so if that salvage part was on its last legs it could have been enough to kill it. This time I've ordered a part that comes with paste included, and I'm going to apply along the entire bottom of the unit in a thin layer.

Also I was just mad, I'll probably never sell this car since it was my grandma's and there aren't many of anything from that era with only 68k miles on it. Had 24k when I bought it from her estate.
 

HotZ28

Full Member
7,098
345
83
Buick Ownership
1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU
"No name coils" are known to fail sooner, than later! Salvage parts should have at least a 30-day warranty. Most Pick&Pull's & JY will replace the units within that time frame if they are an honest reputable used parts dealer. Don't sell the car, fix it!
______________________________
 

OptimistPrime

Buick Newbie
49
8
8
Buick Ownership
Buick
The brand is actually "TRQ" (Trusted Reliable Quality). With a name like that, I'm not surprised they didn't last a week. I put the old coils back on with the new ICM, and the car seems to run fine. I'll be watching it this week to see if it messes up again.
 

OptimistPrime

Buick Newbie
49
8
8
Buick Ownership
Buick
I made it another 200 miles before is started messing up again. I'll get a tester and mess around more with it this weekend. The car has been like this since May and it's really starting to get on my nerves. Every time I think the problem is fixed, it comes back after a few days of driving. Diagnosing an OBD1 car without the right scan tool is infuriating. But there's no way I can afford one of those.
 

OptimistPrime

Buick Newbie
49
8
8
Buick Ownership
Buick
I spent the day driving the car around, trying to get the problem to come back. It drove perfectly, of course. No signs of hesitation. I got a spark tester and started testing coils. What I found was pretty much on par with the video I watched. Each coil had a pulsing light at idle, and solid with throttle applied. However, coil #4 gave a different reading than the others. Occasionally at idle, during the regular light pulsing, it would flash extremely bright. Brighter than anything I had seen on the video, and way brighter than the other coils. I interpreted this as an error state, and swapped on a different coil for the 4/1 pack. Tested and the bright flashing did not return. Drove the car and it seemed somehow better than earlier in the day.

Without knowledge of how to interpret the tester, it's tough to say, but I think that bright flashing indicated the #4 coil was trash. Given the flashing did not return with a separate coil pack on there, it makes me think the ICM is fine. I'll be watching the car to see how it performs this week. It's yet to do a run of serious traffic sitting, so we'll see how it handles that.
______________________________
 
Pedal Commander
Top