406 Hdi fuel consumption

[Paul-R]

Is there any scope for swapping the mafs around to see if the "good" fuel consumption follows the maf?

[Peter.N.]

The fuel consumption improves on both cars if I disconnect the MAF's although the performance drops off on one of them. I am going to test the MAF's when I get a minute, one of them came off my scrap car that was doing 60 mpg.

Peter

[harryp]

Peter, I too drive with a light foot and have (presumably) blocked the EGR as a result. How have you avoided this happening? Foot to the floor occasionally left a huge black cloud behind, the result I believe of carbon from the catalyst due to it not being hot enough to burn it off. When the welds either side of the catalyst went, I was able to tap it onto a hard surface each end and was surprised at the mounds of carbon piled up from either side. Another job to do before it goes back on the road . A very interesting thread and looking forward to the outcome .

[white exec]

Is a blocked EGR necessarily a problem, NOx aside?

[ekjdm14]

Is a blocked EGR necessarily a problem, NOx aside?

Blocked is not a problem, the problem is they tend to not fully block but stick partly open which then causes excessive recirculation and (as far as I can tell) a massive boost leak straight out of the exhaust... Hence the power drop/drivability issues that arise from EGR faults

[white exec]

Of course....makes sense. Not something I have to worry about these days.

[Peter.N.]

Yes I have heard about the possibility of it sticking open but haven't checked yet. I have tried reconnecting and again disconnecting the MAF and it definitely seems to give better MPG with it disconnected although it isn't as much as when I first did it , only a mile or two.

I am going to check both MAFs at the weekend and go from there although it definitely feels as though
one on my wife,s car is working, it came off my old silver one which was doing about 60 mpg and although the journey is the same every day at the moment there are variables like traffic and air temperature which I have found makes a lot of difference, my really good mpg figures were all obtained in the summer. I have a photo of the display on the silver one showing 67 mpg over 500 miles coming home from Scotland, but it was a very hot day and I think the computer was erring on the high side.

Peter