The firing order for most GM 4.3 L V6 engines is 1-6-5-4-3-2.
The exact order helps balance the engine and is critical for properly routing spark plug wires or coil packs, diagnosing misfires, and timing. Note that some model years or ignition systems may vary slightly, so always check the factory manual for your vehicle.
Interpreting the firing order
In practice, the sequence indicates which cylinder fires in each crankshaft revolution. For a typical 4.3 L V6, the order means the first cylinder to fire is cylinder 1, then cylinder 6, then 5, 4, 3, and finally 2, repeating every full rotation of the crankshaft.
To verify on your engine, consult the service manual or a reputable wiring diagram for your VIN. The layout can vary by generation (distributor-equipped vs distributorless ignition) and model year.
For a quick reference, the firing sequence by cylinder is listed below. The numbers refer to the engine's cylinder numbering per GM convention in most 4.3 L V6 installations.
- Cylinder 1 fires first
- Cylinder 6 fires second
- Cylinder 5 fires third
- Cylinder 4 fires fourth
- Cylinder 3 fires fifth
- Cylinder 2 fires sixth
Concluding: This order is designed to distribute power evenly and minimize torsional stress within the crankshaft and engine block. Always confirm with the specific vehicle's manual for the exact layout and ignition system.
Cylinder numbering and ignition system notes
GM's 4.3 L V6 has two banks of three cylinders. Depending on your model and year, the engine may use a distributor, distributorless coil-on-plug, or a coil-per-bank arrangement. The service manual will show the exact cylinder-to-wire mapping for your engine.
Model-year variations
Some variations in firing order are possible in earlier or specialty configurations. If you are replacing ignition components or diagnosing a misfire, verify the wiring by checking the factory diagram for your specific year and engine code (for example LU3, L35, or L35-based families under GM).
Summary
In short, the firing order for the common Chevrolet/GMC 4.3 L V6 is 1-6-5-4-3-2. This sequence helps balance the engine; however, always check your exact model-year diagram to ensure correctness before installation or repair.