[T2] Briefly unresponsive engine - HELP please !!!

[al sinclair]

Please help suggest a cause of a new problem in 1981 aircooled Westie,
automatic not stick shift.

Occasionally there's no response from the engine when pushing the
accelerator pedal to accelerate from stationary. The pedal moves normally,
and the sound of the engine changes so I think the throttle opens, but
there's no change from idle, no increase of power for at least several
seconds. Then the engine behaves totally normally. I've tried pumping the
pedal when this happens but it makes no difference.

The engine was rebuilt a couple of years back (lovely job by Greg Tuttle,
installed by Fred's Garage, runs like a dream) maybe 10,000 miles ago. It's
had oil changes but little else since then.

Any ideas how to identify the cause will be much appreciated. The problem
isn't reproducible on demand, it only happens now and then - and can be
scary if I'm pulling out across the road.

(Above was posted to the vanagon list, where Ned Savoie suggested asking
here.
These ideas came from Larry Alofs there though I haven't followed up as
I've been unwell:

>If an air cooled has a switch on the throttle, I would check that it is
working.
>Also check that the movable vane in the airflow meter is not sticking.

)

Yesterday the same happened again but for several minutes instead of
briefly (well, still brief but it felt like hours sitting in a stoplight's
left turn lane!) So now it's become a MUST FIX ASAP, but tricky as it's
still only occasional

thanks
Alan