Timing problem?Audi A8 D3 4.2 FSI

Hello everybody!

Last days I have a problem to solve. It’s about a fault code named “bank2 camsaft speed sensor”.

I have changed camshafts (put the 3.7l camshafts) because the previous was rusty and could not trust their functionality. I have changed the timing belt set such as many many other parts on this project.

The car have been working without engine problem for over a month since last week…

Then the engine fault revealed. A friend of mine is 100% sure that the timing is not correct. First thing to change was the camshaft speedsensor. Again the fault code after deleting ,showed again,but the car still working nice.

Today my partner that opened the timing belt bay sent me this video.

I ask you if it is logical the timing belt to be so loose and the engine works fine. Seems right or someone could make this happen on purpose ?

sorry for the lots of words but I have lost my mind with this.

If someone please can help, much much appreciated🤟🏻

Hello, the cam belt tensioner has either failed or not been installed correctly it is really as simple as that.

you will be feeling very lucky if it has done no damage to the valves, may luck be with you today,

I thought it looked like the idler on the left, looking at it, had disintegrated, but the closest I can find to your engine seems to have a similarly small guide roller. As Ross suggested, looks like tensioner failure, but there are different cambelt arrangements for the Audi V8, could you have been given the wrong one right from the start, and been shockingly lucky so far?

A Ross said, I'm amazed you don't seem to be suffering terminal valve-to-piston damage!

I'd replace the timing belt and tensioner, and fit all new idlers, time it carefully, and confirm there's no damage with a compression and/or cylinder leakage test. Then, if there's no further damage, I'd give up buying LOTTO tickets for a couple of years, as you've used up your luck for a while :-)