re. 5kcstq low boost, sputtering-bad temp sensor?

Mon May 2 11:17:26 EDT 2005

Thanks so much for your prompt reply Ben!!

>From your diagnostic, I'm now leaning more towards a
bad idle switch, since last time I looked into it,
everything else seem OK.

Last time I trouble shooted it, I left everything so
nice and clean...spotless...and also replaced air
filter and all vac lines around the intake/throttle
body area. And the problem still persisted.  

I did not check the airflow plate as detailed since it
seem quite clean.

I will check everything again and will try replacing
the idle switch with an USED spare one for now.
Hopefully that one is good.

Also what else could go bad if car driven with bad
idle switch?

Thanks again for your valuable insight!!

-Louis

--- Ben Swann <benswann at comcast.net> wrote:

> First I'd check that your idle switch (located under
> the throttle body) is
> working correctly and consistantly.  If not closing,
> then idle stabilization
> circuit is not enabled and engine more likely to
> stall.  However, that said,
> you likely have more than one thing going on.  Check
> all vac lines tight and
> replace questionable ones.  Make sure your airflow
> plate is clean and not
> binding - replace filter and clean all the crap out
> that gets in there and
> underneath the assembly.
> 
> I have had to do this as routine maintenance around
> once a year, sometimes
> it stretches out to 2, but by then I'm having
> problems.  You just can't
> neglect these things forever.
> 
> Once you give everything a good going over, then all
> is well for another
> year or so.  The throttle position switches
> sometimes only last a few years.
> 
> Ben
> ----- Original Message -----
> From: "L DC" <ldc007usa at yahoo.com>
> To: "Ben Swann" <benswann at comcast.net>
> Sent: Saturday, April 30, 2005 11:11 AM
> Subject: Re: re. 5kcstq low boost, sputtering-bad
> temp sensor?
> 
> 
> > Hi Ben!!
> >
> > Hope you're doing well.
> >
> > If I may, I'll like to get your input on a little
> > RPM/idle problem I've been having with my VW
> Quantum
> > Syncro.
> >
> > Is not really an idle problem, I think, since the
> car
> > idles just beautifully.
> >
> > But when I accelerate engine while parked or
> driving
> > up to 3K RPM or more and let my foot off the gas
> pedal
> > (put into neutral when driving and coming to a
> stop),
> > the revs drop to about 200-300 RPMs, and obviously
> > engine sounds as if its going to shut/stall (due
> to
> > the low RPMs), and then quickly the RPMs
> stablelize to
> > its nomal 750-800RPM setting.
> >
> > The problem began a while back, if I recall
> correctly,
> > after I washed the engine (I like to keep the
> engine
> > nice and clean :))
> >
> > Did I break something?
> >
> > I have since inspected the usual hoses related to
> > intake and don't appear to have a leak (dismatled
> them
> > to check each one of them, unless I missed
> something).
> > Also, I have sealed, with silicone, the idle
> adjusting
> > screw, just to make sure there's no leak there,
> just
> > in case.
> >
> > I also replaced the ISV with another used one?
> Could
> > that be the problem?
> >
> > But if so, like I said the car idles just fine
> except
> > when I rev it up to 3K RPMs or more and then let
> my
> > foot off the gas pedal either parked or when put
> into
> > neutral while driving.
> >
> > Your input is greatly appreciated!!
> >
> > -Best Regards,
> >
> > Louis
> >
> >
> >
> > =================================================
> >
> >
> >
> >
> > --- Ben Swann <benswann at comcast.net> wrote:
> > > More plausible is that you have a simple intake
> > > tract leak - most likely an
> > > opening at the bottom of the Intercooler to
> Throttle
> > > body hose aka.
> > > "Michelin Man hose".  You often can't see these
> > > without removing the hose
> > > and throuroughly examining as the opening oft.
> > > occurs under a metal ring.
> > >
> > > Don't get all complicated about the diagnosis -
> I
> > > always hear about clogged
> > > cats, but have never really seen one and I have
> > > looked at a lot of them -
> > > not saying it doesn't happen.  I have on the
> other
> > > hand seen/diagnosed these
> > > symptoms.  You have an intake leak which is
> messing
> > > with the Idle
> > > stabilization as well as throwing off your
> mixture
> > > and causing boost(metered
> > > air) to be bled off.
> > >
> > > Ben
> > >
> > > [Date: Thu, 28 Apr 2005 14:29:48 -0600
> > > From: barry at moonbeast.com
> > > Subject: 5kcstq low boost, sputtering-bad temp
> > > sensor?
> > > To: quattro at audifans.com
> > > Message-ID:
> > > <1114720188.427147bce6d90 at sec.moonbeast.com>
> > > Content-Type: text/plain; charset=ISO-8859-1
> > >
> > > Hey gang-
> > > It's been awhile since I've posted, hope
> everyone's
> > > doing well.  I seek your
> > > wisdom once more.
> > >
> > > My '87 5k is almost sorted out now, but I've
> still
> > > got some gremlins that
> > > I'm
> > > trying to exorcise.  Here's the major issues:
> > >
> > > 1. I'm consistently seeing low boost - in normal
> > > driving, not usually more
> > > than
> > > 0.9bar, and not more than 1.2bar at WOT.
> > >
> > > 2. Sputtering at idle.  By messing with the idle
> > > adjust screw at the front
> > > of
> > > the intake manifold, I can balance it between
> > > wanting to stall and going
> > > into
> > > the infamous "idle bounce" mode where the engine
> > > speed rises, cuts out,
> > > falls
> > > then rises again (ISV and its hoses have been
> > > replaced).  The exhaust is
> > > sputtering at idle, even though the car is
> smooth on
> > > acceleration and at any
> > > road speed.
> > >
> > > 3. The water temp gauge shows full cold pretty
> much
> > > all the time.  It has
> > > risen
> > > to half scale on occasion, but unpredictably. 
> Most
> > > of the time it stays
> > > pegged
> > > on full cold, even after more than an hour at
> > > highway speeds.
> > >
> > > 4. Fuel economy is crappy- I get about 19mpg
> > > consistently, on rare occasions
> > > topping 20.
> > >
> > >
> > > My (admittedly inexpert) guess at this point is
> that
> > > the water temperature
> > > sensor has gone bad, and the system never gets
> out
> > > of "cold start" mode.
> > > It's
> > > constantly running that intake manifold
> injector,
> > > which makes the system
> 
=== message truncated ===

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