Scraping/hissing sound when lifting foot off the gas?

[DamInc]

Hi all,

Have 55 plate CDTI 150 Estate. Have had a few problems with it since I bought it last year leading to the following work:

No 3 injector replaced
DPF removed and remap
New EGR Valve
New No 3 injector connector

The last change was on Thursday night and he car was transformed from a juddering lump when accelerating to a mostly smooth, much more pleasant drive.

The car still seems to have the odd issue though. Before the EGR replacement and connector change the car developed a sound. When accelerating with a bit of pressure and releasing the pedal to change gear there's a sound which sounds like a scraping/hissing sound. If I accelerate lightly there's no sound. The car, at low revs still also feels a little lumpy/uneven when accelerating but I could be being paranoid with that as I'm now expecting the car to have an issue all of the time.

I've seen a post on here stating a similar noise could be the flexi pipe at the front of the exhaust? Anyone have any experience of this? I also get a smell of fumes in the car at start up. All related? Cheap to fix? If I leave it (this car has cost me a bomb so far, so need to wait a few weeks before I can spend more on it) will that be an issue?

Any advice gratefully received.

[DieselWig]

The fumes smell could be from the exhaust and the flexi section is the most likely - you should be able to feel the exhaust gas escaping (don't burn yourself doing it though) if someone revs it. Also the flexi section will likely be blackened from the escaping gases.
The fumes could also be from the EGR or the EGR connection hoses, so check these too including any gasket leaks.
Both of the above may make a hissing noise I suppose, but this noise could also be from a split hose to the inlet manifold or the intercooler although these may whine rather than hiss.
I would find the exhaust fumes leak first and then see whether it also fixes the hissing noise.