Northstar Ign Coil/module failures
 

Hi folks...is it just me, or is there a known issue with the ignition coils/module on the earlier( ie '94 era) Northstars? I'm on my 3rd set of coils, and module. I put new plugs and wires on last summer along with 2 different coil/module sets, and this week I lost another coil, which fouled two plugs. I don't remember off hand what AC/Delco plug range I use, but it's whatever is recommended in the FSM, and the plug wires are also AC/Delco.
A little history on this car...
The car was brought in to a repair shop to have some work done. The engine was hammered, and the owner didn't want to fix it, so he gave up the title. The guys at the shop asked me if I wanted to buy the car, since they know I'm into Cads. I declined, since I didn't want to get into installing an engine, but a guy that worked at my shop bought it. He paid someone to install a "salvage" engine, which didn't work. They put in another salvage engine that also didn't work. In the end, he took the best parts of the first two engines and made one, with new heads, pistons, and crank. I bought the car from my guy the day they got it running. It's always ran great, except for when one(or more) of the coils takes a dump.
Is there something specific that I am over looking that would cause this kind of repeated failure? The car never fails emissions testing...matter of fact, it's exceptionally clean.
Any idea?

Ignition coils modules don't have a high failure rate it does happen. Most of GM's trial and error was done during the mid 80's in the V6 cars. Normally cars that have repeated failures of a particular part or system have power/ground or connection troubles. If you are getting used parts it could be bad luck they were already marginal when you got them. Check ground under car at lower crankcase on passenger side also condition of ICM connectors. High resistance of plug wire(s) can causing miss which if ignored can cause COIL/ICM failure.

Thanks for the tips. I have an ign module tester that will fire the coils, and they will all ohm out ok with my DMM, considering that ohming don't really mean they are any good. I guess the ground issue is prolly more likely, since they did pull/install the engine three times. A-huntin I will go!:D

what was wrong with the two engines?
what car model are we looking at?


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Sorry...I thought I said...:o
I'm having this issue on my '94 SLS. I'm not sure exactly what the two "salvage" engines had wrong with them, but the original had cracked heads, water in the oil, and rattled quite nicely. The (original) owner simply didn't want to fix it. A guy I worked with at the time bought it, and had the other engine work done. All I can say is I bought the car from him the day they finished the engine work. This was 2005, btw. He never specified what problems the two engines had. :)
Other than this repeated coil failure, the only other thing I've done is replace the water pump a year ago...it had a small leak. The car runs great, and has since I've had it.


btw...the only time it has ever set any engine related codes is when the coil(s) fail. Then, it will set a MAP sensor code...I chased that one for a week before I realized the code was setting because of the low vacuum signal due to the dead cylinder... DOH!

Update on this... It's been wet/raining here for a long time, so I haven't been able to do any checks on the coils/module. I think there is probably a ground issue. I also have the factory TSB/Recall manual/book that has a TSB on replacing the ign module, and making certain that the correct module is installed. Seems one type of module has a black painted base, and the other is natural aluminuminum...and of course, I have a few of each type....therein may lie the problem.... I'll let ya know what I find as soon as the weather co-operates.

the car is running on a mix of the two?

yeap .. I say there you have two places to start.

Well...no...not at the same time. I have a couple of the black base modules, and a couple of the natural modules. I just never paid any attention to which one was on there at any given time. I would just replace it with the next one I had. I don't know for sure which type is correct/original, since the engine was changed, and the module with it. I did get the left-over module when I bought the car, but...I don't know which one was original to the car. I have also bought a couple since then. The TSB calls out a VIN break, if I remember correctly, so I'll be going by that when I get the time to check it more thoroughly. :D