Dear Marcus,

My '84 GL did the same thing as yours.  I fixed mine by disconnecting a wire
on a metal contact switch located just behind and to the right of the
throttle on top of the engine.  You could also lower the RPM of your engine
to fix this, but many older vans need higher RPMs to keep the engine cool.

In the factory repair manual, the contact switch is called a "throttle valve
switch."  If you have a factory repair manual, turn to page 24.33 and look
at the picture.  The manual says the switch "supplies control unit with
information that throttle valve is closed.  If engine is running 1500 RPM
with the throttle closed, fuel will be shut off to the injectors."

What's happening is that when you let off the gas, the throttle switch
closes.  Your rpm is over 1500 so the control unit shuts off gas to the fuel
injection system.  As rpm's fall below 1500, fuel is again sent to the
injectors.  This on/off of gas to the injectors is what makes your engine
pulse.

The switch has two wires that plug into the back end of it.  I disconnected
one of the wires and my engine now runs smoothly.  Warning, there is another
switch nearby called the "full throttle enrichment switch"  which, according
to the manual, "supplies the control unit with information to increase
amount of fuel injected at full throttle."  See page 24.34 of the factory
manual, top left.

If you don't have a manual, first find the throttle on your engine (the gas
pedal cable connects to it so it moves when you press the gas pedal).  Look
just to the right and behind the throttle.  The switch you want to
disconnect is on top, and the wires plug in on the rear of the switch (the
side closest to the front of the van).  The switch you don't want to
disconnect is underneath and closer to the rear of the van.

Best of luck to you.  Any questions, feel free to write me.

Preston Lewis
'84 Vanagon GL