Date:         Mon, 06 Jan 1997 17:01:40 -0800
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Tonya Pope <galba@premier.net>
Subject:      Re: Rough running when Hot

Hi!

Larry and Dan already pointed out good things to check (don't know about
Karl--didn't have to go that far on mine--but it is a cheap thing to
try).  I went through the ordeal for quite a while, but mine had to cool
down after it acted up before it would act right again.  You can test
the O2 sensor by unplugging the single wire that connects to it (there
are 3 wires altogether, 2 go to one plug, 1 goes to another).  That's
the signal wire.  If that improves your situation, replace the sensor. 
You don't need to fork out the $120+ on the VW part, a good, generic
3-wire will do--write me and I'll explain or you might find it in the
archives--I've explained the steps before, as have others.  Don't really
want to drive around with it unplugged for long (i.e. more than a few
days) because it will affect performance and gas mileage.  It is there
for a reason.

Vacuum lines wear out over time and even if they look good, the ends
might have enlarged to where they let in a leak once hot.  Hard to
diagnose, but only a couple bucks max to replace all of them.  Look
around the air intake boot too.  I had a leak there and had to replace
the boot.  Boot is around $115 (seems like everything I replaced trying
to fix my beloved vanagon cost $115!)

Another possibility is the coolant temperature sensor that goes to the
computer.  That was mines' problem.  Once it got to a certain temp, the
sensor was telling the computer that the engine was too hot.  Thus, the
computer, in a life-saving maneuver, cut the fuel supply.  Voile, loss
of power, bucking, kicking, etc.   This too is cheap.  Part is around
$12 (with little o-ring that you need) and VERY simple to replace.

If yours is starting right up and performing after misbehaving, it may
need the magical harness.  Again, you'll find it in the archives and in
the technical bulletins.  Basically, the air mass sensor confuses the
computer from time to time.  VW made a little 'adder' to insert in the
wiring.  Very simple, unplug old connector, insert new and plug it all
up.  Unfortunately, expensive.  Part runs around $115 or so.  Try other
suggestions first.  There is a cheap, under $1, fix as well that is
explained in the archives or bulletins somewhere.  VW's part is little
more than a couple of cheap electrical components wrapped in this nice
rubber connector.  Not worth nearly what they charge (except for the
fact that it makes some vans run!)

Good luck, hope everything runs smooth soon!

Tonya
87 Vanagon GL Wolfs
74 S. Beetle