A thumping heard and felt in the floor is often caused by failing engine mounts. A failing mount allows too much movement of the engine, and will require replacement.
Problems for specific Nissan Quest years:
Car problem reports
Problem with your car? See what our experts say or submit your own.
Repairpal verified 2001 Nissan Quest problems
The distributor shaft bearing can become rusty, and seize causing the engine to stall or not start. The failed distributor will commonly require replacement.