Date: Mon, 4 Oct 1999 16:03:14 +0200
Reply-To: Darie Duclos <Darie.Duclos@UNIFR.CH>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Darie Duclos <Darie.Duclos@UNIFR.CH>
Subject: 1/4 mile syndrome is back!
Content-Type: text/plain; charset=us-ascii
Help!
I thought this problem had gone away, but now that I've got
road inspection this week, it turns out it's not solved. I
have a pretty good description of the symptoms now. Perhaps
you can help me narrow down the possibilities.
The problem: accelerator pedal begins to have little or no
effect on propelling the vehicle forward. When the speed
has dropped sufficiently, the engine hiccups forward, as
if I wasn't giving enough gas. The RPMs go down, so it's not
something like the clutch slipping. It may feel like it's
running of fewer cylinders. Without even stopping, I can
turn off the ignition and right back on, and the acceleration
is back for 1/4 to a 1/2 mile, then the same thing happens
again.
Important details:
- when engine is cold, no problem, I can start it up and
drive with no apparent time limit so long as I don't turn
it off.
- each time (3 or 4 times) the engine was running between
10 and 30 minutes, then *was cut and started again* (with or
without much of a pause), the problem occurred: I had to
cut the ignition and restart every 1/4 mile until my
destination.
- after a *45* minute drive (from cold start of course),
cutting the engine and starting again several times, with
varying delays, did *not* reproduce the problem.
- arg! I just tried to reproduce the problem again by driving
5 minutes and shutting off the engine, then restarting.
It won't do it! It only does it when I really want to
go somewhere!! Damn piece of merde.
- the engine is running much too rich. (At least) when it has
the problem, it spits out coal, enough to make a serious
black stain on the pavement or on your pants if you're standing
behind the bus.
- a car electrician just checked some values related to the
temperature sensor. He found that at 40 degrees it read
1200 somethings (ohms? I can't remember) but he couldn't
find my model of bus in his references and he didn't know
for sure whether this value was normal. I left him my
Haynes manual but I don't know if it's in there. Anybody
know what this value means and what it should be for an
86 2.1 liter water-cooled vanagon (MV)?
The only thing for sure about this problem is that it has never
occurred on a first run after cold start. It has only happened
upon starting up the engine when already warm. And then, if it
starts doing it, it does it at every startup. If it doesn't do it,
it doesn't do it at all no matter how many times I restart.
The following possible causes had been
suggested after my previous postings. I would like some opinions
about which could be ruled out because I have very little time
until the inspection and I'm afraid that if I take it to a garage
it will cost me an arm and a leg before they even figure out what's
wrong.
- fuel pressure (pump or regulator)
I changed the fuel filter with no effect. How can I test the
pump or regulator?
Wouldn't this cause a problem upon a cold startup or during
an initial run?
- bad O2 sensor
We disconnected and reconnected the O2 sensor once, before the
45 minute test drive, to see how the bus ran. Then we tried to
reproduce the problem with the intention of disconnecting the
O2 sensor at that time and see if the situation improved.
Unfortunately, after driving 45 minutes, the problem did not
occur.. I plan to try this after a shorter drive, but I'm not
sure what I should expect. i.e. it's runs bad, I disconnect the
O2 sensor, it runs better? Some of you said it wouldn't run very
well with the O2 sensor disconnected so how do I tell the difference?
- bad temp II sensor
Would this not cause a problem even without cutting the engine,
simply just when the motor gets warm?
I can see how some of these things would get reset upon restarting
the engine and I heard that their values are ignored by the
"computer" for a little while after startup, but I don't see why
they shouldn't affect the "first run" after the motor has gotten
warm.
- grounded O2 sensor circuit, loose or disconnected O2 sensor ground
I may have twiddled it both times when the problem could not
be reproduced. How could I check for sure that this is the
cause? I guess the car electrician could do something with
measurement instruments but I have to reproduce the damn problem
for him, which I just failed to be able to do.
- clogged catalytic converter
Shouldn't the problem be more constant then?
- faulty ignition switch
Is it dependent on the warmth of the motor?
- gas cap plugged up
my gas cap is not ventilated, but maybe some other ventilation
is plugged up. However, the pattern of the symptoms speaks
against it again.
If you can help me narrow down the possible causes, I would be
very thankful. Also, if you can point me to the procedure for
incriminating or innocenting one or the other component, that
would be great.
I'm kind of on my own (swf) to do this now since I moved out of
the pretty-good-with-mechanics-boyfriend's place yesterday. I'm
not very experienced but I can do anything I'm told. (Hey, I changed
my pilot bearing a few years back with your help..) And I've got my
Haynes manual..
Thanks a bunch!
Darie
'86 multicolour canadian Westy with swiss landed immigrant status