I just thought I'd post my experiences in case anyone may benefit. I'm a Laguna II owner, specifically a DCi Expression 100bhp registered in Feb 2004. It's fully dealer serviced it now shows 112k miles, I bought it with 85k on the clock.
I found this forum back in November when my car first began hesitating and later began illuminating the glow plug preheat warning and the toxic fume warning lights. Up to that point I'd not had a single problem with the car.
As the hesitancy got worse I checked various forums and narrowed the most likely problem to the
valve so I initially set out to clean it. After taking off the engine cover and various obstacles I realised that the electrical connector on the
looked like that plastic that gets brittle with age. None of the forum notes mention whether there's a latch on this connector or if it just needs a tug (could someone post that info if they know - someone else will find it helpful). So rather than risk damaging it I decided to put all the items back on and try to find an alternative method or someone else to clean it.
All the posts say that if it's faulty its likely to be coked up so I figured that maybe an engine treatment may work. I got a bottle of Wyndehams Diesel Injector treatment, I figured if it works in the cylinder it should continue to have an effect a few inches along the exhaust path. Its a small purple bottle and over a couple of weeks (I don't use the car that much) I added a bottle to a half tank of diesel. That's double the recommended dose but it seemed to do the trick. Fuel consuption was terrible (down to 25mpg) but over a couple of weeks the worst of the problem went away. There are similar brands out there but I'm used to their products so that's what I chose.
The other change I made was to stop using supermarket diesel. Instead I used the BP or Shell premium diesels which contain detergents to keep the engine clean. I figured the 10p extra per litre over a tankfull works out at about the same as a bottle of the fuel injector treatment so it seems like money well spent.
I had to to a 300-plus mile round trip to Sheffield soon after in early December and that may have helped blowing out the junk in the system. That run went wityhout problem. On my car the hesitancy issues used to be most apparent when going uphill under load but that hasn't happened for well over a month now, in fact it's running perfectly.
If you've found this thread and catch the problem early then maybe try this first. It's certainly cheaper than an
valve change or a blown
As an aside I now recognise some of the characteristics of the premium diesels. BP Ultimate and Shell's version both work really well, much smoother running with much less knocking apparent. Texaco Excellium on the other hand made the engine feel decidedly rough. And I haven't used supermarket own brand diesel since November. If it goes pop I'll post again but so far so good.