[Biturbos4] Throttle position sensor problem

[Tony Hoffman]

Richard,

I've also dealt with this on customer cars, but never a v6tt. I've had
to clean the TB's on the 1.8T's and the 30V 2.8 and 3.0's. Do it just
like Grant described. I use Brake parts cleaner, then WD for a
lubricant. However, if you use brake parts cleaner, be very careful
where you spray it. i can melt/eat certain sorts of plastic. Only
allow it inside the throttle body itself.

Tony

On Sun, Oct 26, 2008 at 10:17 AM, Grant Lenahan <glenahan at vfemail.net> wrote:
> BTDT on my 2000 S4.
>
> here's what I found.
>
> The typical fault you will get is called "epc" and a light should
> come.  epc is electronic pedal contgrol, or drive by wire.
>
> When a fault in the fly by sire system is detected the system goes
> into limp mode, which you experienced. It was happening to me every
> day. It resets with an ignition cycle.
>
> What i found is that the throttle butterfly, which is controlled by a
> stepper motor, slowly builds up crud inside the TB, much like an old
> carbon composition potentiometer in a hifi. I posited that thsi was
> the case, and tried the same old cure:
>
> 1. clean with carb cleaner by spraying inside the TB
> 2. loosen/clean the TB inside by exercising the butterfly completely
> through its angle of motion, several times, quickly. This creates a
> wiping action.
>
> It worked.
>
> You can infer that one of the problems I had run into was that teh S4
> basically had too much power for normal driving, and i almost never
> went WOT.  So junk built up.  Its another case of cars must be driven
> as intended, at least occasionally.
>
> Hope this helps,
>
> Grant