* Engine Management System (EMS): The 2004 model likely has a more advanced ECU and wiring harness than the 2002 model. These are not typically interchangeable.
* Sensors and Components: Specific sensors, mounts, and other components might have different placements or specifications.
* Transmission Compatibility: The transmission bolted to the 2004 engine might not be compatible with the 2002 transmission.
To determine if it's feasible, you'd need to:
1. Identify the exact engine codes: Find the engine code (e.g., 3.5L 3500) for both the 2004 and 2002 Vue engines. Slight variations within the same displacement can create incompatibility.
2. Compare engine specs: Look up detailed specifications for both engines. Even minor differences in the block, heads, or other components could prevent a successful swap.
3. Consult a mechanic specializing in Saturn Vues: A qualified mechanic can assess the feasibility and the extensive modifications (wiring, mounts, potentially even machining) that would likely be required.
In short, while it *might* be *theoretically* possible with extensive work, it's far more likely to be a very difficult and expensive undertaking, potentially more costly than finding a used engine specific to the 2002 model year.
