New member, and needing help with my 2009 Lacrosse V-6. 93,000 miles, 3rd owner and haven't had it long. At first it was a strong runner, but a few months back it stopped me cold, near my house. I came back hours later, still no start, dorfed around in the fuse box, swapped a few 10 amp fuses and it started. It has generally run poorly since and barely drove it since. Now that salt is off the roads here (I have a separate salt dedicated car), I want to drive it. The trouble code is General Misfire.

So now: new plugs and wires, they appeared original. No change. Three new coils. No change. Here is where it gets interesting. If you picture the coil stack, it goes (top to bottom) 6 3 2 5 4 1. Start the engine...idling with the new coils. One at a time, I can connect a high energy spark tester to each coil tower. Disconnect 6 and there is no test spark and no change in stumble. Do that to all the others and there is spark at the high energy tester and the stumble is worse. One by one, I install each original coil in the 6 3 (top) position and I never get a spark in #6 and .... NOW I don't have spark from either 6 or 3 tower to the spark tester with any of those coils installed temporarily.

What is wrong? The PCM? A signal wire from PCM to that coil primary? If #6 injector is not functional, is the PCM so intelligent that it doesn't fire #6? Are #3 and #6 coil towers designed to fire at the same time (waste spark)?

Your help would be very very much appreciated. I am very open to probing wire traces from PCM to coils. I don't yet know where the PCM is located.

Car is pretty nice, although it has seen a lot of salt (no body rust through though) and I have invested a bunch of time in exhaust, front suspension and brakes.

 

I poked around You Tube and learned that the coils are sitting on a power circuit board called the Ignition Module. Bought a new one, installed it and there is no misfire.