Throttle switch

[Jens Knickmeyer]

<Seth Allen> wrote:
> 
> On Thu, 1 Aug 1996, Jens Knickmeyer wrote:
> 
> > Date: Thu, 1 Aug 1996 14:39:33 +0200 (MET DST)
> > From: Jens Knickmeyer <knick at ibr.cs.tu-bs.de>
> > To: EFI Mailing List <DIY_EFI at coulomb.eng.ohio-state.edu>
> > Subject: Throttle switch
> > 
> > Hi all!
> > 
> > In my Polo-G40, I found the idle throttle switch to open
> > _before_ the throttle plate moved. When I had a friend of
> > mine pressing down the accellerator pedal, I heared the
> > click of the switch and shortly after that, the throttle
> > started to open. I always thought it should be the other way
> > round: the throttle opens a bit and then the switch opens
> > its contacts?
> > 
> > The reason for my question is a problem during warm-up.
> > The engine starts perfectly, runs good during post-start
> > enrichment, but then suddenly acts a bit reluctantly.
> > When I press down the accellerator pedal only a little
> > bit, the engine revs 100rpm below its normal idle rpm.
> > Accelleration from idle rpms lets the engine tend to stall.
> > These effects vanish when the engine is warmed up.
> > 
> > I wonder if the idle switch is adjusted correctly. The
> > VW service men said yes, but it would not be the first
> > time they are wrong, so I thought I'd better ask the 
> > list members...
> > 
> > Any help is apprciated, thanks in advance.
> > 
> > Jens ('92 VW Polo-G40)
> > 
> > ------------------------------------
> >            Jens Knickmeyer
> > Technische Universitaet Braunschweig
> >          Mikroprozessorlabor
> >  38106 Braunschweig near Wolfsburg
> >        knick at ibr.cs.tu-bs.de
> > ------------------------------------
> > 
> > 
> Hi Jens-
> 
> I have only minimal experience with the g-lader motors.  Just a few US- 
> spec G60 corrados.  Only when cold?  It could be carbon build up on the 
> back of the inlet valves like the old VW-audi problem in the 1970's.  You 
> could try adjusting the base idle with the 7mm brass scew in the throttle 
> body (don't do it with the throttle stop). If this car has digifant, then 
> I don't have much help to offer other than this. If it has CIS-E then you 
> may even be able to fix it!
> 
> Good luck, 
> 
> Seth Allen
> Western Washington Unversity  (Vehicle Design)  

Seth,

thanks for your answer. Seems you are right about the carbon. A VW mechanic
told me the same, and so I burned my engine free by driving not under 
180km/h. I did this at 11.30 pm when the Autobahn was not so full any more.
Helped a lot - the car runs a lot better now, no stall on accelleration
any longer. Think I will repeat such a "burn free" a few times.
Yes, my car has digifant. I am reverse engineering the ECU to find out
how the diagnostic interface works. Yuo know, the DF has an OBD and 
can transmit the fault codes to the VAG1551. Also, you can do such nice
things as switching off the lambda and idle control loop to allow a
basic setup of mixture and ignition timing. But that's another story...

Thanks again for your advice!

Have fun,

Jens ('92 VW Polo-G40)

------------------------------------
           Jens Knickmeyer
Technische Universitaet Braunschweig
         Mikroprozessorlabor
 38106 Braunschweig near Wolfsburg
       knick at ibr.cs.tu-bs.de
------------------------------------