Ford Repair: throttle ???, ford explorer xlt, downhill slope

Question
Hello James, I'm trying to troubleshoot a problem with my 2004 ford explorer xlt 4.0 liter. When I release the throttle on a downhill slope, I feel a lurching motion as the compression begins to slow the vehicle down. It varies from barely noticeable to heavy similar to a low or flat tire. I've never  seen anything like it before so I'm not sure where to begin. any help you can give would be great. thanks

Answer
Start by telling me details like when did it start?Does the truck run normal otherwise?If so have the compression tested.It could be just a bad case of the too much compression,which isn't considered a bad thing.Most people see that as a good thing.Let me know how the trucks runs and any abnormalities if applicable.