The firing order is 1-4-2-5-3-6.
The 2008 Lexus IS250 uses a 2.5-liter V6 (4GR-FSE) with a six-cylinder layout. The firing order describes the sequence in which the spark plugs ignite in each cylinder, a detail that matters when replacing ignition components, diagnosing misfires, or testing the ignition system. This sequence helps ensure smooth engine operation and proper timing across the engine’s two banks. The following outline provides the standard sequence and how to apply it to maintenance tasks.
Firing order sequence
To aid maintenance and troubleshooting, the order in which cylinders fire is shown below in the established sequence from first to last. This helps technicians map spark plug and coil positions to the correct cylinder numbers.
- 1
- 4
- 2
- 5
- 3
- 6
Understanding this sequence is essential when replacing ignition coils, spark plugs, or wiring harness sections, and it assists in diagnosing misfires by confirming that each cylinder fires in the expected order. Always verify with the official service manual for your exact engine code and production date to account for any market-specific variations.
Cylinder numbering and verification
The IS250’s V6 uses the standard Toyota/Lexus approach to cylinder numbering. For maintenance tasks, rely on the factory service manual or OEM diagrams to identify which physical cylinder corresponds to each number (1 through 6). If you are replacing ignition components or performing timing-related work, confirm the exact cylinder mapping for your vehicle’s engine code and model year, as diagrams can vary by production run and market.
Practical tip: disconnect the battery and follow torque specs from the service manual when removing or installing spark plugs and ignition coils. Using the correct sequence and torque helps prevent misfires and ensures reliable engine performance.
Maintenance considerations
Verification and documentation
Always cross-check the firing order and cylinder numbering against the official Lexus service documentation for your vehicle’s VIN and engine code. If in doubt, consult a certified technician or Lexus dealership to confirm the exact diagram for your car.
Summary
The 2008 Lexus IS250’s V6 fires in the order 1-4-2-5-3-6. This sequence is critical when servicing ignition components, diagnosing misfires, or performing timing-related work. Always refer to the OEM service manual for the precise cylinder mapping and torque specs, and verify any model-year or market-specific variations before beginning work. Maintaining adherence to the correct firing order helps ensure smooth engine performance and reliability.