Took my Vanagon to get smogged today.

The mechanic there could not get it to idel at 2700 rpm. The bus 
would rev at "smog testing level - a certain RPM" then cut-out. A 
second later it would rev at"smog testing level" then cut out.  This 
continued for as long as he held the throttle at the rpm.

He whipped out his stephascope and listened to the exhaust system, 
and could find no leak.  Hmmmmm

This problem does not come as a surprise. Everyone has a method of 
telling when their bus is warmed up. Mine has been when this 
reving-then-cut-out occurs. ( The coolant needle is in the far left 
box when the above occurs. 

Any ideas????

Matt