In brief, the firing order depends on the engine: the base 3.8-liter V6 uses 1-6-5-4-3-2, while the high-performance 5.3-liter V8 used in the Impala SS uses 1-8-7-2-6-5-4-3.
The 2004 Chevrolet Impala could be equipped with two powertrains: a standard 3.8-liter V6 and the sportier 5.3-liter V8 in the Impala SS. Knowing the correct firing order is essential for spark plug servicing, distributor timing (where applicable), and diagnosing misfires or timing-related issues. Below is a breakdown of which order applies to which engine, based on typical 2004 Impala configurations.
Engine options in the 2004 Impala
The following sections cover the firing orders for the two engines commonly found in 2004 Impalas.
3.8-liter V6 (3800 Series II)
Firing order for this engine:
- 1-6-5-4-3-2
The 3.8-liter V6 in the 2004 Impala follows a traditional GM V6 sequence that is widely used across the 3800 family.
5.3-liter V8 (LM4) in the Impala SS
Firing order for this engine:
- 1-8-7-2-6-5-4-3
This 5.3-liter V8 used in the Impala SS (and related GM vehicles from that era) adheres to the Gen III/IV firing order commonly used on that family of engines.
Summary
In the 2004 Impala lineup, two firing orders apply depending on the engine: 1-6-5-4-3-2 for the 3.8L V6 and 1-8-7-2-6-5-4-3 for the 5.3L V8. Always confirm the powertrain on your specific VIN and consult the factory service manual for exact timing procedures and any model-year variations.