I have an '85 Volvo (I will get to the Vanagon content in a sec.) with the
same type of problem. It has a Bosch L-jet ( I think) fuel injection system.
I too replaced the fuel pump, worked for a while, fuel filter, didn't help,
Air Mass Meter ($225) worked for a while. Initially the only constant I
found was  the "break" in the electrical. Both with the replacement of the
fuel pump and the AMM the circuit was broken and it ran better afterward.

I have also noticed that hotter weather makes it worse. My problem all but
dissapears in the winter, but comes back in the summer..

One thing I have found that lasts longer than turning off the key is to
disconnect something while the vehicle is running, and then reconnect.. I do
the AMM because it is quick and easy.

NOTE: I DO NOT KNOW IF  THE ABOVE IS OK TO DO ON A VANAGON BUT IT WORKS ON A
VOLVO!!

So, about 2 years ago a listee of the Type2 variety told me he had a similar
problem with, guess what?? a Vanagon! Anyway his fix was to replace the temp
sender. I have not tried this on my Volvo because the temp sender is in a
tight spot and I can live with this problem right now.

Bentley gives a chart on how to test it by comparing it with some data from
the air flow senser and coolant temp. pg 24.45
Personally, I don't understand what they are saying to do, but maybe you
will or someone else can help replace it.

Hope this helps.
-Chip

Steven Johnson wrote:

> Greetings!
>
> I'm seeking input on a recurring problem with my '87 Westy.  A few
> months ago, I wrote concerning the van's propensity to suddenly lose
> power while running.  I took it to the TLM (trusted local
> mechanic--specialized in VW's) and one new fuel pump later, the problem
> disappeared.
>
> Well, it's back.  I was on my way out of town the other day, and the
> same problem reared its ugly head.  Here are the details:
>