My 90 failed the California smog test today. In short, the idle values
were off with HC ppm at 424 where max allowed is 120  though the 2500rpm
values passed fine and are way below limits.

So I am looking for some clues on where to start with this, and while I
realize it might not be straight fwd, thought I would see if anyone has
some insights. Replacing components one by one might get expensive so i
was hoping on narrowing it down on what it **could be.

Idle is fine though it has been rough for a while at startup and I have
had intermittent, what appears like missing at high speeds when
accelerating.  I had thought that i was seeing what folks refer to as
the "vanagon syndrome"  but with with the idle values like these am
thinking that it could be as a result of  the idle control valve (though
it vibrates), the idle control unit or the coolant temp sensor (which i
am told can cause a rich mixture.

It looks like Bentley has clear steps to trbl shoot the idle though I am
not sure, without the proper tools, if I can make the needed adjustments
it calls for.

Thanks in advance for any wisdom that can be shared..!!

-john