My son's 89 Buick Lesabre t-Type ran good all summer. Now it will just die and you never know when it will. But it never fails to start back up. Can be going 45 down the road and just die on you. Any ideas on this, Have checked fuel filter. My brther seems to think coil pack/module or computer. Any thoughts appreciated. I hate to just start wasting money buying parts that aren't gonna fix it. Thanks.

 

May want to check the crank sensor...best thing to do is hook up am oscilloscope and check the pattern while its running...if it loses signal, then problem solved...the older gms also did have problems with the ignition control modules...

 

I had an '87 LeSabre with a 3800 that did something similar - it was the mass air flow sensor. It was idling erratic only after driving at lights and stuff and would shut off. But it always restarted and ran fine until driving again. Seemed good under initial throttle, decent power, then rough idle, stall... MAF fixed it

 

I'm gonna go out on a limb here...

My neighbor has a 1989 Buick his did the very same thing...
Turns out it was a failing fuel pump....

Maybe...
You could a fuel pressure gauge up to it that you can Monitor as your driving...? Then when it does fail... you'll know one way or the other.

 

I know there is a large difference in tech and age, but my dad and I have been chasing a similar prob on my step-mom's '00 Grand Am. Actually, I think it is 2 issues. One pointed to the ICM (and we had a spare and swapped it).
Shortly after the ICM swap, it began stalling and would not restart, but as your goofing with it (normally next day), it would restart. Right now she's not driving it and we're going to do more during spring.
I drove it around town to further diagnose as I came up with an idea (and when I drove it, it was when if it died, no biggie, I could work around it). Next time it stalled, I noted the starter would not crank, dash lights would not come on, instrument cluster would not activate, but things like the radio worked. We were thinking it's the ignition switch. Next time it died, since the car has remote start, I would remote start it (as all systems need to do there thing). Sure enough it worked (it would die as soon as I hit the brake, it was about 7 stops, 2-3 minutes from dad's place, I drove it home on the remote start and ebrake when roads were not busy).

Any case..... Could be an ignition switch (but since it restarts, I'm not feeling that). I like Jerry's thought.... Wiring around the coils and ICM. I'd also see if a local parts store could test the ICM.

This might help troubleshoot the coils:
Comprehensive guide for troubleshooting Ignition coils : Powertrain (Ignition, sensors, etc)

FYI - If I recall, that coil one large coil unit (a Magnavox coil). I believe their is a way to convert it to a modern ICM/Coil combo that is much better. If you have to replace the coil, that might be a mod to consider....
Swapping your Magnavox Ignition to the delco Type II system : Performance

Best of luck!!