Offroad-Express

Yeah, 4wd will make horrible noises if it is engaged on hard surfaces

What you thought was tappet noise probably would have been the timing chain rattling. May indicate poor servicing.

The 2.0l 4 cylinder Vitaras are supposedly desirable. Good engines when compaired to the V6's. I don't think those engines have timing chain issues but running old or wrong grade oil does cause the engine to rattle. Mine use to rattle bad on startup, changed the oil and it quietened down.

Yeah don't engage 4x4 on grippy surfaces like clean concrete and asphalt unless the car has a centre diff, those Vitara's don't. The front wheels have to travel a longer distance than the rear wheels and without a center diff to take up the distance difference either the wheels will skid or something will break.

The J20A uses a timing chain.