Firing order diagram please?

1986 BUICK PARK AVENUE
86,000 MILES • 3.8L • 6 CYL • AUTOMATIC
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NETT86
I can't figure out the spark plugs sequence I need a diagram please.
Sep 9, 2025 at 1:44 PM
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STEVE W.
  • ASE Certified Mechanic
  • 15,171 POSTS
  • ASE Certified Mechanic
The coils on that car use a waste spark system, It fires two cylinders at the same time but one produces power while the other is on the exhaust stroke. This makes it easier to deal with the plug wires. Each coil gets two cylinders 1 and 4, 5 and 2. 3 and 6. The image and coloring show the paired cylinders. As to the exact order, as long as 1 and 4 go the first coil, 5 and 2 to the second and 3 and 6 on the last one you are fine. IE you can have them as shown, or you can reverse 1 and 4 locations, as long as they stay on that first coil.
Some of the coils will even have the numbers cast in the coil.
Sep 10, 2025 at 1:05 AM
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