* Specific Engine Code: The exact engine code stamped on the block (usually near the oil filter) is crucial. Different codes might have variations in components like intake manifolds, sensors, and even internal parts that prevent simple swaps. Finding a donor engine with the same or a very close code is key.
* Year of the Vehicle: Engines from other years *might* fit, but you'll likely need to adapt wiring harnesses, computer modules (PCM), and potentially even some engine mounts. The closer the donor engine's year is to 1997, the better the chances of a relatively straightforward swap. Expect more issues the further you stray from the 1997 model year.
* Transmission Compatibility: Make absolutely certain the donor engine is compatible with your Sunfire's transmission. Mixing and matching engine/transmission combinations can lead to major problems.
In short, while engines from other years *might* be physically compatible (with modifications), the easiest swap will be with an engine from a very similar year Sunfire or another GM vehicle using the same 2.2L Ecotec engine and code. Researching the exact engine code on your 1997 Sunfire is the first and most important step before considering any replacement engine. Look for the code on the block itself or in service manuals.
