Lincoln debuted the LS in 2000, as a direct competitor to the BMW 3 Series and the Mercedes-Benz C-Class. In 2005, the LS had two engine options. The base engine was the 3.0-liter V-6 with 232 horsepower, and the optional engine was the 3.9-liter V-8 with 280 horsepower. There are two main numbering sequences in regards to the spark plugs, and those are the cylinder numbers and firing order.
Cylinder Numbers and Firing Orders
On the 3.0-liter engine, the cylinders are numbered 1-2-3-6-5-4, starting from the front, passenger side of the engine and moving clockwise around the engine. The firing order of the V-6 engine is 1-4-2-5-3-6. The 3.9-liter V-8’s cylinders are numbered 1-2-3-4-8-7-6-5, starting from the front, driver side of the engine and moving clockwise around the engine. The V-8’s firing order is 1-5-4-2-6-3-7-8.