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I have a 2008 Buick Lacrosse CXL with the 3800 Series 3.I am having a no spark issue on cylinders 3 and 6. The back ground is this. The wires are only 2 years old and I bought the AC Delco wires. The plugs are AutoLite Iridiums (I know I know, not OEM, but 3800’s love these plugs).
I have troubleshot this down to the coil pack or the Ignition control module. The question I have is I know the Ignition Control Module is supposed to put out a voltage of 10 to 12 volts. Mine is putting out 14 volts when I hook up the volt meter to this.
Being in IT and a former Computer Repair tech, I know that too much voltage can do just as much damage that not enough. Is this reading okay? Or does it mean that the Ignition Control Module is putting out too much juice and fried the Coil Pack.
Could it be that when its cold (which the engine is and the car is outside and it is 20 something here) that it puts out move voltage for more spark? I didn’t notice on my W-body and my coworkers that these cars start at 14 volts at start on the inside meter and after they run a bit, the voltage meter in the car will mellow out to 12 to 13 volts. So it seems like it could be regulated down once warm. Did I just answer my own question?
I did test this while the engine was running and I got a steady 14.5 volts out of it, but this was just turning it over and then turning it off after testing.
Thanks for any insight you can give.
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I cannot seem to find in my information what the exact voltage to the icm should be, but hook your meter up and watch it while at idle, and while increasing the rpm’s. Then compare it to the voltage coming out of the alternator. As far as your miss, sounds like the one coil, that fires cylinders 3 and 6 is dead.
Well, I figured it was the coil, so I bought one and put it on. Well that didn’t fix anything. I know that its a no spark issue as I pull the plug wires off this coil and it does nothing to how the engine is running. I figure the control line is dead for the top circuit. I am going to get it into my parents garage where all the tools are and take it apart tomorrow.
Since the alternator of any given vehicle is cranking out 13 to 14.5’ish volts, I wouldn’t worry about that reading. Automotive electronics (save for the IC’s in the ECM which may take only 5 volts) are not super sensitive to variations.
It isn’t unlike 3800 series 2 and 3 engines to eat coil packs. The likelihood that you need a new ECM are pretty slim, but does sound like a new coil is needed.
You COULD disconnect the battery which clears the codes, swap the positions of two of the coils, connect battery, fire up engine and then see if you start getting codes for misfires on different cylinders. Right now I assume you have codes P0303 and P0306? You say you swapped that coil for the 2-5 coil, then codes p0302 and p0305 would come up. PERHAPS. I don;t remember exactly what cylinders are fed by the other two coils, if they are 1 – 4 and 2 – 5 but you can figure that out real easy.
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