Why would your 99 Cadillac Escalade lose power on long hills and pulling a load?

A 1999 Cadillac Escalade may lose power on long hills and while pulling a load due to several factors, including a weak or failing engine, fuel delivery issues, or a clogged air filter. The engine may struggle to generate enough power if it has low compression or if the spark plugs are worn. Additionally, an inadequate transmission or overheating issues can also contribute to reduced performance under load. It's essential to check for diagnostic trouble codes and inspect the vehicle's systems for a comprehensive diagnosis.