Hi my xj lags when i step on the gas only on 4x4. When I switch i step on it it takes a second to start moving

 

More information is needed. Does it do it in 4L as well? So you need to give it more throttle to make it move? If you apply light throttle does it lag or just sit there? Like sitting on a steep hill and applying throttle but the vehicle stays still? And I assume you have an automatic?