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.
Nissan Quest Problem Reports
RepairPal Verified Nissan Quest Problem Reports
A coolant leak may develop from a plug on the front of the rear cylinder head, behind the timing cover.
A creaking or clicking heard while the vehicle is accelerating can be caused by dirt and corrosion build up between the splines of the front hubs and CV axle shafts. Removing, cleaning, and applying a light coat of grease on the axle shaft splines will commonly correct this concern.
The distributor shaft bearing can become rusty, and seize causing the engine to stall or not start. The failed distributor will commonly require replacement.
The exhaust manifold often warps and cracks, breaking off the studs between the cylinder head and the exhaust manifold. The noise may be most noticeable when the engine is cold.
The fuel injectors can fail and cause drivability problems. Often there is no Check Engine light and the failures can be caused by corrosion of the connector, clogging beyond the point of cleaning, and/or internal failures.