This means that the spark plugs fire in that order, starting with cylinder #1 and ending with cylinder #4.
Here's a breakdown of the firing order:
* Cylinder 1: Front of the engine, driver's side
* Cylinder 5: Rear of the engine, driver's side
* Cylinder 3: Front of the engine, passenger side
* Cylinder 6: Rear of the engine, passenger side
* Cylinder 2: Next to cylinder 1, driver's side
* Cylinder 4: Next to cylinder 6, passenger side
Important Note: Always verify the firing order for your specific Mustang model year and engine size. This information can be found in your owner's manual or online resources.
