Potential Issues and What to Do:
* Wiring Harness: This is the biggest hurdle. The engine harness connectors may be slightly different between the 1998 and 1999 models. You might need to splice wires, use parts from the 1998 harness, or even get a custom harness made. This is best left to someone with wiring experience.
* Computer (PCM): The 1999 PCM will likely be incompatible with the 1998 car's sensors and wiring. You'll almost certainly need to use the 1998 PCM or get the 1999 PCM tuned to work with the 1998 car's components. Professional tuning is highly recommended here.
* Sensors: While generally similar, minor sensor variations are possible. Double-check that all sensors are compatible, or source replacement parts as needed.
* Exhaust System: The exhaust manifolds and potentially the catalytic converter may not be a direct fit. You may need to modify your existing exhaust system or source a used one from a 1999 Mustang.
* Transmission: If you're swapping the entire engine/transmission assembly, ensure the transmission is compatible with both the 1999 engine and the 1998 car's bellhousing and other drivetrain components. Automatic and manual transmissions are not interchangeable without significant modification.
* Mounting: While the engine block itself should fit, there might be slight differences in accessory placement or mounting brackets that require minor adjustments.
In short: While the engine itself is very similar, the supporting systems (wiring, computer, sensors) are where the challenges lie. This is not a simple swap for a novice mechanic. It requires a good understanding of automotive electrical systems and engine management. If you lack experience in this area, you'll need to hire a qualified mechanic.
Before you start:
* Gather information: Research your specific 1998 and 1999 Mustang models (engine codes, transmission types, etc.). This will help you identify potential compatibility issues.
* Acquire the necessary parts: Don't start the swap without having all the necessary parts (engine, transmission, wiring harness, PCM, etc.).
* Consult a professional: If you're not comfortable with the complexity of this project, seek help from a qualified mechanic specializing in Mustangs. It'll likely be cheaper in the long run to pay a pro than to make costly mistakes.
This project is significantly more complex than just swapping engines – it's a full engine *and* systems integration project. Be prepared for a considerable time and cost investment.
