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.
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.
