D4204T Help! V50 2.0D, intermittent power loss - no fault codes

[Martin_Butcher]

Hi,

I have a V50 2.0D (05 reg) which I bought at the turn of the year with about 25k miles on the clock. With the exception of the below, its a lovely car.

However ... on several occasions the engine has experienced a significant power loss as described below. I have read a lot of posts on this board, but none of them quite match up so I have posted the below to see if anyone can offer advice.

The symptoms are like this:

1) Driving along normally - say 60ish in 5th gear,

2) You accelerate, and as you are accelerating suddenly the engine power just disappears - but no warning lights, messages etc.

3) Back off the revs, engine power comes back so you can maintain speed, however if you start to accelerate again and demand more power, again the engine power will disappear

4) This will perhaps happen 5 - 20x if you keep repeating the above sequence but then the car returns to normal and all the power you can want (without needing to stop the engine). Then it won't happen for another month or so.

Now last time this happened (nice straight bit of the fosse way!), I noted that at the same point the engine lost power you could hear a sound of releasing air (a bit like when you release a pump from a tyre) coming from the engine compartment area.

I took the car into TMS Volvo in coventry and no fault codes. They inspected various parts (not sure what) but the summary was bring it back when it becomes repeatable.

Would welcome any thoughts.

My thoughts at the moment are:
1) Its not a problem that generates a fault code (that must narrow it down some, unless diagnostics has failed as well)
2) It probably not a hose as that would likely happen all the time, not happen for 5 mins in the middle of a journey and then mysteriously disappear.
3) urrrm??

I would be most grateful for any help!

Thanks,

Martin