For over a year, my Vanagon engine has been surging badly, especially when
the accelerator is fully depressed, as it frequently is at highway speeds.
The rate of surging at highway speeds is approximately 2 cycles per second.
The surging can be minimized by backing off at bit on the accelerator, but
since the engine is underpowered for the vehicle, it is not acceptable to
use anything less than maximum acceleration.  At street speeds it is much
less noticeable but even then there is often unsteady acceleration.  It
makes driving unpleasant and rough.  Sometimes the problem will suddenly
cease and there will be smooth running for anywhere from a few seconds to
several miles, but otherwise, it is there most of the time.

It is a 1982, originally diesel, but converted before I owned it to what I'm
told is an 86-92 Rabbit/Fox engine.  The computer has Bosch number 0 280 800
104 (105) on it.  It is fuel injection.

I have been told by two different seemingly competent shops that the problem
lies in a part numbered Bosch 0 438 101 005, which I believe is called a
fuel flow meter or a fuel injection pump.  Not sure of that...I'm not a
mechanic, as must be obvious.

The first shop to work on it had it back at least 5 times before they gave
up.  They tried cleaning and adjusting that component to no avail.  They
couldn't get a new part and tried replacing with a used part and said the
other used parts performed worse than my own.  They also replaced the O2
sensor.

The 2nd shop said replacement of that part would cost me $2000 because the
part is not made any more.  They offered to do an engine conversion to a
Suburu for $12,000!

Can you tell from the symptoms if this part is really the culprit?  Is there
any way to replace this part at a reasonable price?

Thanks very much in advance.

Paul Chubbuck in Fort Collins