Date: Fri, 19 Jul 2002 23:09:21 +0100
Reply-To: Clive Smith <clive.harman-smith@NTLWORLD.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Clive Smith <clive.harman-smith@NTLWORLD.COM>
Subject: Re: future is looking bleak....
Content-Type: text/plain; charset="iso-8859-1"
>I have learned since, that a bad ground, even one, can screw the ECU up so
bad that it either runs in "closed loop" which defaults to a mixture that is
rich (ie, hot exhaust pipes) or can simply screw the small voltage signals
up enough to make just about any related componant just act plain old
screwy.
Rich mixtires do not lead to hot(ter) exhaust running, weak ones do as burn
slower and thus threaten the exhaust valve as it opens. 'Popping back on the
overrun' (as its called in the UK) is often caused by a weak muxture still
burninga s the exhaust valve open, the weak mixture being a result of an
idle throttle setting and a fast overrun, e.g. going down a hill with the
foot off the throttle in alow gear, or after just having selected one for
braking purposes. Rich mixtures are more prone to actual detonation
(dangerous high power detonation), weak to general upper cylinder
overheating which can either a) incite pre-ignition (pinking) b) burnt
exhaust valves c) possibly lead to detonation under some circumstances. As
with all things engineering - there are few hard and fast rules, grey areas
generally prevail and thus a thorough understanding of the interplay of
sometimes contrary effects is required - I've just picked up a few along the
way.
Clive Smith
'88 Syncro Transporter
----- Original Message -----
From: "Robert Steven Fish" <fish@SALZBURG.CO.AT>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Friday, July 19, 2002 11:07 PM
Subject: Re: future is looking bleak....
> -----snipped-----
> It does seem to be idling and picking up much better at first, but after
> picking up speed and then when coming to a stop and then accelerating
again
> it's the same old thing. No response after stepping on the pedal till I
mash
> it to the floor.
> -----end snipped-----
>
> One other thing that I forgot to mention... In the process of
> troubleshooting my vanagon syndrome, with a racing idle at 2500 or so,
that
> would not go down anymore (used to go away after a restart of the car...
> then not even.. but would disappear randomly... then constant 2500 or so
at
> idle, which is not really so nice in city traffic at stop lights) was taht
I
> replaced a bunch of things at the same time... so I really do not know
100%
> what was causing the problem. I replaced, in addition to the AFM, the
Idle
> Stabilizor Unit (valve) and the COntrol unit (the electronic box located
> behind the right reaaar taillight).
>
> But the one thing that may have made all the difference in the world was
> randomly finding that the main engine to chassis ground strap (drivers
side)
> was toast. It was a crumbled oxidized mess of dust. I replaced it with a
> nice 1cm thick length of Monster speaker cable, and made certain that all
> the contacts were clean and happy.
>
> I have learned since, that a bad ground, even one, can screw the ECU up so
> bad that it either runs in "closed loop" which defaults to a mixture that
is
> rich (ie, hot exhaust pipes) or can simply screw the small voltage signals
> up enough to make just about any related componant just act plain old
> screwy.
>
> Check all your grounds.. but do definately also check that idle switch on
> the throttle housing... it is relatively easy to check (not so easy to
> adjust precisely though). You can hear/feel it go "click" when the
throttle
> is full open or full closed... at all other times it should be off, and
then
> the ECU will be in charge (so if your ECU is screwy, it could manifest
> itself in the inbetween position I guess).
>
> Good Luck!
>
> RSF
>
> IMPORTANT!!! In order to reply to me, you must have the word "FISH"
> somewhere in the subject line of the email. Otherwise it goes directly in
> the trash.
>
> <º)))>{ <º)))>{ <º)))>{ <º)))>{ <º)))>{ <º)))>{
>
> Robert S. Fish
> Salzburg, Austria
> 1987 Wolfsburg Vanagon 2.1 GL Weekender
> 1987 Golf Cabriolet
> 1991 Golf
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