I have a stock 2.1 watercooled engine that runs well, but consistently
idles at 2000 rpm. What should it idle at and how do I adjust it? I've
recently replaced the coil, distributor cap and rotor, plugs, wires, air
and fuel filters. Is this something I should just leave alone and be
grateful that my van is running at all?(snip)
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IMHO, First and foremost, I would look for some sort of intake vacuum leak.
Grab an old w!ndex bottle, and fill it with some soapy water and spray around
the airbox, manifolds,etc.. and see if you get a drop in the idle.

Unless you or someone else played with some screws in the engine bay, I would
bet it's an air leak. The air intake boot can crack along the seam on the
back side, so be sure to check there first;)

C.B.