I've had that problem too, and I was able to fix it by adjusting the
idle per Bentley:  Disconnect the idle stabilizer plugs and plug them
together.  Then adjust the timing and idle to specs (650 rpm I think)
and reconnect the stabilizer.

The idle speed is adjusted by turning the screw adjuster located on the
throttle body (NOT the one covered by a plug on top, that is the mixture
screw).  It controls the amount of air that bypasses the closed throttle
valve to allow for idling.  In my case I had to adjust the idle down,
which was what the idle stabilizer was trying to do in its own way, but
couldn't hold it steady.  Hence the cycling.

There has to be extra air coming in from somewhere, so if this doesn't
fix it check the crankcase breather hose, that can also loosen and
crack. Keep looking for vacuum leaks until you find one (or more!).

Good luck!

Stuart

Martin wrote:
>
> Hi All,
>
>    I'm having trouble with the idle on a didget.  The idle is erratic and
> goes from 1500+ to an immediate drop to 1000 and continually cycle quickly
> like that.  I did the test for the aux air valve as per Bentley and it
> pointed to that.  I have been driving with that hose pinched off and it
> idles and starts just fine.(20-50F)  When I replaced the aux air valve, the
> same symptoms appeared so I pinch off the hose again.  I am getting 12+
> volts to the air valve.  The air valve closes out of the van with 12v
> connected, as it should.  I could not find any vacuum leaks.  My tail pipe
> is blacker than normal and mileage might be down 1-2mpg.  The temps sensors
> were fine.  I did not get a chance to check the fuel reg. yet, that's next.
>   Any ideas?
>
> Thanks,
> Larry