1. Injector Design and Fuel System:
* 1996: Used a simpler, less-refined injector system which was prone to leaks and failure. They were also more susceptible to damage from contaminated fuel.
* 1999: Featured redesigned injectors with improved spray patterns, leading to better atomization and combustion. This resulted in more efficient fuel burning and reduced emissions. The entire fuel system saw improvements in reliability.
2. Turbocharger:
* While both years used a turbocharger, there were likely subtle improvements in the 1999 model's turbocharger efficiency and design to better manage boost pressure and enhance performance. Specific details would require consulting factory specifications.
3. Engine Calibration (ECU):
* 1996: The engine control module (ECM) programming was less sophisticated.
* 1999: The ECM programming was refined to optimize fuel delivery, timing, and other parameters for improved performance, emissions, and fuel economy. Emissions standards were becoming stricter, demanding better control.
4. Exhaust System:
* While the fundamental layout likely remained similar, the 1999 model might have incorporated minor changes to meet stricter emissions regulations. This could include changes to the catalytic converter or exhaust gas recirculation (EGR) system.
5. Other Minor Differences:
* There might be minor differences in sensors, wiring harnesses, or other ancillary components due to ongoing engineering refinements and cost-saving measures. These changes are usually not readily apparent without a detailed parts comparison.
In Summary: The most significant differences between the 1996 and 1999 7.3L Power Stroke engines lie in the fuel injection system and the overall engine calibration. The 1999 engine generally represents an improvement in reliability, fuel economy, and emissions compliance over the 1996 version, but both are known for their durability. However, pinpointing *every* small difference requires deep diving into the Ford factory service manuals for both years.
