Something I think I know just enough to be dangerous, but not enough to be
helpful.

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My van is doing the following and I need some ideas:

- lots of sputtering at idle.  My van barely maintains idle and nearly
dies.

- blackish smoke is coming out the tailpipe (its not super thick, but it
is certainly noticable).

- I can hear some "knocking" noises in the engine.  Not sure what this is
but there is a distinct knock-knock-knock noise.

- I think I hear valve clatter that is different from the above knocking
(but I'm not 100% sure I know what valve clatter is).

- When driving down the road, it surges a bit, but not so bad I can't go.

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Here is what I have done (some of these probably don't matter, but I'm
trying to be complete)

- adjusted the valves.  Some of them felt very soft.  After starting up
and hearing even more valve clatter, I readusted the valves and tightened
the "soft" ones even more.  This seemed to help both the valve clatter and
the van seemed to run better, but it was still bad.

- checked the timing.  It seems ok, but its hard to tell with poor running
at idle.

- new plugs, cap, rotor today.

- new air filter.

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Help!  Any ideas?
Thanks,
Blake
SLC, UT
84 Westy