05 2.0d Intermittent power loss - martin butcher

I have a V50 which is still in warranty and has a intermittent loss of power fault, perhaps every 500 miles.

The symptoms are:

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 the main dealer where I bought it from and no fault codes. They inspected various parts (not sure what) but the summary was bring it back when it becomes repeatable.

The position I am in at the moment with Volvo is that they can't fix it until it happens often or it logs a fault code. Its not doing either!!

Any thoughts on what the problem may be, or how I get the garage to be more helpful than 'there's no fault code, we can't fix it'.

I am concerned I will be left high and dry by Volvo if the warranty runs out and this is still happening.

Thanks in advance,

Martin Butcher
05 2.0d Intermittent power loss - craig-pd130

I suspect that what you're noticing is the DPF regenerating. What makes me think this is, it happens only once per month or so (I'm guessing that's about every 500-600 miles).

On my own Mondeo IV with DPF, throttle response goes very woolly when regenerating and although the engine WILL pull if you boot it, it feels a little unhappy doing so ... rather like an old carburetted, manual-choke car used to when stone cold on a winter morning.

The hissing noise is probably a combination of a) the cooling fan running, which it will do automatically when a regeneration is happening, to help remove underbody heat from around the DPF casing and b) the different intake noise caused by the movable flaps in the inlet manifold closing (this restricts airflow into the cylinders to promote the "coking" of the soot in the DPF).

Again from experience with my own car, regenerations are more seamless and barely noticeable now after 18 months and 15K miles. In the first few months of ownership they were much more noticeable.
05 2.0d Intermittent power loss - martin butcher
Hi Craig,

thankyou for your reply, this is a good comparison as I think these cars have the same engine.

I will try booting it next time this happens to see if this helps. To date, it has felt more like someone has turned the fuel of when you try and accelerate above a certain point so have not booted it, just backed of and limped along for 5-10 mins then the problem has gone away (without restarting).

The other thing to note is that my car has done 25k miles (its an 05) so hopefully it would have been well into the seamless stage. Perhaps of note is that we do 1/2 of our miles running around locally and then a longer journey (200miles ish) once every month.

I could see how the hissing noise may be caused by flaps moving. It doesn't sound like the cooling fan. The noise sounds like opening a can of coke.

If I am driving along and have just experienced this power loss problem, you can make it repeat by slowing down and accelerating up again. This noise happens at exactly the same time as the car loses power.

isn't this all fun!

Thanks for your input,

05 2.0d Intermittent power loss - martin butcher
Well, the car has been in today and had new software loaded in the engine management unit and the DPF filter regenerated.

Volvo have also confirmed that a new EGR valve was fitted before we bought the car.

Let's hope this has done some good.