Input/Turbine Speed Sensor

As far as I am aware (I could be wrong!), neither Volkswagon or any other manufacturer of cars with Turbos is interested much in the speed of the Turbo, they only need to know the volume and temperature of the air being supplied by the Turbo.

To do this there is a special sensor, a hot wire I believe, that is monitored for current flowing through it. The cooler the wire, the lower the current, the more air is going by it and cooling it down.

They get dirty and then need replacing, the problem shows itself as a lack of engine power, especially low down in the rev range. I know, I have been there, got the T-shirt and worn my clutch as I was in the mountains with a heavy trailer when it made itself visible......

A blown off Turbo air supply pipe gives a similar impression, only even less available BHP and a noticeable change in under bonnet noise!!! I have had that several times too!!

It was an expensive item then (2003 and before) as the whole unit had to be replaced, but I believe the modern versions are made that only a smaller cheaper part must be replaced. If your car is less than about 3 years old, I believe that the cheaper version will be available (Note I did not say "cheap" on its own!!)

If its any consolation, Mercedes and other companies have had exactly the same problems.....I beleive that the sensors all come from the same supplier....

Changing to a Mercedes version gives a noticable increase in avalable BHP (It was in the German press that some had done just that as the Mercedes version was much cheaper than the VW version, but of course your guarantee is null and void!!!

Go to www.vwvortex.com

Find the forum for your year. (Mark III or Mark IV) or (A3 or A4)

Do a search on the forums for P0715.

Never trust a car made after 1984.

My previous comments may have nothing to do with your problems, my apologies if that is the case, I was just going on the infos supplied and remembering problems I had with a VW Sharan Turbo Diesel that I once owned. Air volume sensor is the one in question.....

The problems (I was not alone) received a lot of motoring press attention at the time.....

Have a great day anyway!