For the 4.2L V6 engine (VIN U) in your 2008 Ford F150, the firing order is:
1 - 4 - 2 - 5 - 3 - 6
Verifying Firing Order on the Engine
- Cylinder Numbering: The front cylinder on the driver's side (left bank, closest to radiator) is Cylinder 1. The front cylinder on the passenger's side (right bank) is Cylinder 2. Numbering alternates banks moving rearward: Driver's side: 1, 3, 5 (front to back). Passenger's side: 2, 4, 6 (front to back).
- Ignition Coil Pack Terminals: The coil pack has terminals labeled with cylinder numbers. This is the most reliable reference point for verification.
- Spark Plug Wire Routing: While the firing order determines the sequence, the physical routing of the spark plug wires matters less than ensuring each wire connects the correct coil pack terminal to its corresponding cylinder. Wires are often different lengths to prevent crossing/routing errors if installed properly. Focus on terminal-to-cylinder connection, not wire path appearance.
Critical Considerations
- DO NOT rely solely on a diagram here. Visually confirm the cylinder numbers cast into the engine's intake manifold near each cylinder and match them to the labels on the coil pack terminals.
- Connecting spark plug wires to the wrong coil terminal is the most common error, leading to misfires, rough running, and potential damage.
- An incorrect firing order will cause immediate severe engine misfire and won't run properly.
Always double-check connections against the coil pack labels and cylinder head markings.
