Intermittent running

["K.G. Nicholson" <kgn@domain.elided>]

I have one of those very annoying intermittent faults and would be grateful to
hear the ideas of the list as to the possible cause.

The problem only occurs when the engine is warm.  On acceleration in high gear
at low revs the engine momentarily stops and then starts again. Usually this
occurs only once but on some occasions will do it for three/four times
resulting in a kangarooing down the road!  The majority of the time the car
runs beautifully with good fuel consumption and even tickover.  At higher revs
(above 3000 rpm)  there is no problem.

Initially I suspected ignition but this has all been replaced/checked out. 
Since the fault occurs only on acceleration at low revs I now suspect a fuel
fault.  However I find it strange that a fuel fault would have such a sudden
stop/start symptom. (could both carburettors be wrong at the same time?)

The float heights have been checked and the float chambers are clean.

The car has been run around for a week by a top specialist who did not manage
to get it to misbehave but it really needs a long run (50 miles) before the
fault shows up. 

Any thoughts would be appreciated since this fault spoils an otherwise great
car.

Regards 

Graham Nicholson
For Tony Gee and Partners