[Biturbos4] Throttle position sensor problem

Richard van der Hoff quattro at rvanderhoff.org.uk
Wed Nov 19 14:52:41 PST 2008

Hi guys,

A quick update on this fault... After the suggestions here, I gave the 
throttle body a good cleanout with carb cleaner (it was indeed full of 
gunk,on closer inspection), and also gave the tracks in the 
potentiometer another cleanout with contact cleaner. I also found that, 
on a previous dismantling attempt, I'd omitted to tighten one of the 
hose clips on the intake plumbing, which would probably explain the 
"pressure positive deviation" fault... doh!

After all that, I still had a fault light, and the VAG-COM now indicated 
that one of the sensors wasn't working at all. Take it all apart yet 
again... and I found a break in one of the connections inside the pot 
body - a bit of soldering later and it's working again.

It's been a few hundred miles, and so far so good. I'm not quite sure 
whether the original problem was that connection beginning to go, gunk 
in the TB, or failure to tighten the hose clip - but either way, it all 
seems good now, so thanks all for your help!



(I might even think about putting the plastic covers back on the engine...)

Richard van der Hoff wrote:
> Hi guys, and thanks for the suggestions.
> The symptoms are exactly as you describe, Grant.
> Brett Dikeman wrote:
>> On Oct 26, 2008, at 11:17 AM, Grant Lenahan wrote:
>>> 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.
>> 1.Make sure to use throttle/carb cleaner, not brake cleaner, which could 
>> destroy plastic bits and does not contain any lubricants.
> Noted. I have to say, I've had the TB off and wiggled it about plenty, 
> and it looked fine and in no way gunked up. Also I don't think my 
> problem is never driving it at WOT (for better or for worse...). Still, 
> it sounds plausible (especially after 170k miles) so I'll get hold of 
> some carb cleaner and try as you suggest.
>> 2.If you can get to the potentiometer, hit it with Caig's MoveIT moving 
>> contact cleaner.  If it is an enclosed potentiometer, really get it 
>> covered- some will work its way in to the contacts.  Actuate it a bunch 
>> of times, then use compressed air to blow it clean, repeat once or 
>> twice.  As long as the tracks are just dirty, it should work great 
>> afterwards. If they're damaged, well...then you're kinda screwed, unless 
>> you can find a very close replacement for the pot.
> The pot does come apart and the tracks look fine. I've tried "normal" 
> contact cleaner on them...
> Do you have a link for MoveIT? I couldn't find it anywhere, including on 
> Caig's website. Do you mean DeoxIT?
>> Since gunk will affect the resting position of the throttle, it may be 
>> beneficial to re-calibrate the throttle?
> Tried that already :/.
> Thanks again,
> Richard
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