A3 tdi (BLS) Revving without applying any throttle?

[Chalkymon]

I'm a wksp owner & currently have a very strange fault on a customers 09 A3 tdi. (BLS eng.code) Everything has been looked at but it's proving difficult. The symptoms are particularly noticeable in 1st & 2nd but can also happen in higher gears. As you're about to change up a gear the engine revs run away, sometimes quite dramatically? Almost as if the engine decided to accelerate hard! This is NOT the clutch switch! Nor the clutch itself. The fault can occur without touching the clutch pedal. It's right at the moment when you would anticipate depressing the clutch whilst lifting off the throttle at the same time (As you would in any manual transmission car) Before either of the pedals are moved the engine revs increase with the added sensation of the turbo creating boost, this in no way is corresponding to any added throttle pedal input? It's an extremely odd fault to diagnose, even the local Audi Main Dealer is at a loss as to what the Hell is going on? Like I said previously this is not a clutch issue! I'm starting to think the throttle pedal assembly might be a suspect but I'm not in the habit of guess & spend when it comes to fixing my customers vehicles. Any info about this fault would be greatly appreciated.

 

[Jcbmally]

Once heard of the electronic throttle assembly having grit//dirt causing a signal issue, on diagnostics it was ok but they changed the unit anyway. They later discovered it was confirmed as a bit of dirt/grit in the "petonchameter" I've no idea how you spell it !!!
Just a thought !

 

[Chalkymon]

Thanks for your input mate. I removed the throttle pedal assembly & stripped it down as far as I could but nothing obvious was found. I do still have a suspicion it is faulty. It's going to be one of those nasty on-going hunts for clues.