Been out and caught this on video for you guys.

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Again, same relatively flat dual carriageway, sustained WOT and no gearshifts.

You can see the fuel pressure dip and recover and also a corresponding dip and recovery in the engine RPM.

Possibly a sticky fuel pressure regulator. It could be opening and closing too slowly. Ive cured this in the past with Dipetane which is a fuel system cleaner and lubricant. I put in a heavy dose to clear the issue then use it periodically since. Cheap enough to try.
Trouble is ultra low sulphur diesel has lower lubricity than before. You could also try 2 stroke oil in the fuel.
Is it still slow to pick up from standstill. 2007 Vogue TDV8 in Zermatt Silver with Charcoal

Ill order some dipetane to try.

What would you consider to be a suitable heavy dose? I fill the fuel tank once every 5 days so should i dose when full or?

When pulling away normally from a stop there is lag on the accelerator as into it to get moving but there is a 1, 2 pause before any reaction.

The same occurs when slowing down and turning off into a road.

Off the power, on the brakes, slown down and turn into the road, back on the accelerator 1,2 pause before the power feeds back in

Are you just seeing the pressure being backed off from its maximum, as per the extract from the WSM below?

The high-pressure fuel pump can supply up to 1700 bar fuel pressure continuously with short excursions to 1750 bar. Pump speed is 5/6 engine speed. However it is calibrated to deliver fuel pressure dependant upon engine speed and load and is always under full control.

In PSI that difference is approximately 730 psi (1750 bar down to 1700)

Whereas i seem to be dropping from 24360 right down to 18415 and then recovering at WOT


I could be very well be barking up the wrong tree with this train of thought but we are nearly all out of ideas

What if the fuel pressure sensor is faulty in that it is intermittently overstating pressure? Perhaps inspect the electrical contacts of both the connector and the sensor for corrosion.

It appears that the sensor at least originally was not a spare part, instead included with a new rail. However the sensor can be purchased after-market.

https://www.ebay.co.uk/itm/LAND-RANGE-ROVE...2773512708


Edit: Seems more likely the pump is backing-off because less power is required.

Standard dose for Dipetane is 200:1. I put half a litre into a quarter tank of diesel and drove briskly for 30 odd miles keeping the revs up. Then added diesel to what was left in tank and dosed as normal. It will at least rule that out and clean and lube the fuel system for around £10.
Its good stuff.
As for your symptoms, it does sound similar to the trans issues I had. (Separate issue to the sticky regulator) A flush, filter and after 200 miles or so a reset sorted it. The thing is, I didnt notice how poorly it picked up until I had a remap done. It is entirely possible that you didnt notice either and hose split made you more aware. Wait and find out what the ZF chap says on that one.
Has the trans been serviced that you know of. What mileage is the car. Edit just read first post again, over 100k miles. 2007 Vogue TDV8 in Zermatt Silver with Charcoal

The RR is now on 105k miles, i serviced the box about a month ago using genuine Zf fluid and filter to see if it would help. The old oil was quite clean and the magnets in the sump had very little build up on them.


Personally I don't think its a case of not realising and become more aware of the issues as I am very tuned into the way my car drives. I thought it drove really well and then after the remap it was fantastic to drive, very eager and instantaneous even in normal driving.

Just spoken to the gearbox specialist and other than a firm 1-2 shift (which has always been present at least in my ownership) they can't fault the gearbox. As ive already changed the fluid/filter there isn't anything more needing to be done.

So we are down to the drop in fuel rail pressure. Dipetane and an Italian tune up. 2007 Vogue TDV8 in Zermatt Silver with Charcoal

Mm having re watched my video and thinking about it I think i could be mistaking the drop in fuel pressure for a gearchange lowering the engine rpm.

Dipetane arrives tommorow so hopefully give it a run over the weekend.

Thankfully i get to use my far better car on Sunday for the festival of 1000 classics at Chomondeley castle.

Diptane in the tank today and went for a run up into the hills. God its awful at higher altitude.

Very lethargic and laggy.

Now 6 months and 7000 miles later with no sign of a cure in sight.

No idea what to do with it as I don't feel like I can sell / part ex it like it is at the moment.

Both specialists who drove it / inspected it couldn't feel what I am complaining about. If anyone is based around Manchester, Crewe or Sheffield areas I invite you to drive it and help confirm the problem isn't me!

worse at altitude would indicate a maf sensor.
Have you tried unplugging one at time and then both and see what you get. 2007 Vogue TDV8 in Zermatt Silver with Charcoal

I have tried unplugging one and then the other and there are just barely noticeable changes to how the car drives. Unplugged is definitely worse though.

The RR barely moves with both unplugged.

Ive tried cleaning them and swapping in a new genuine part in various combinations.

The test done by a specialist did indicate higher flow than expected on the n/s MAF but this could be a remap side affect.

The problem is I don't have any data to compare to

If the place that provided the remap has a dyno then maybe get them to test and diagnose.