The symptoms you describe sound exactly the same as the issue I had with my RRS TDV6 2010 when I had it. Check out this https://www.disco4.com/forum/topic160401.html

I realise yours is a TDV8 so not sure if above is relevant. I lubricated my TSOV with WD40 and grease. unplugged the vacuum a lot of times to activate the valve and problem never recurred for the 18 months I had the car afterwards.

Hope its of use, good luck.  2016 L494 SDV6 HSE Dynamic Carpathian Grey

Thanks mate for the info, I need to get someone to look at this, I’m bu@@ered at present and it will be several weeks before I’m able again. 👍 ________________________________________
2008 HSE RR Sport TDV8 Stornaway Grey

Inlet manifold split, rear area of left bank, now that I know what’s wrong I can rest easy, in hospital, will need to plan the repair now, something to occupy me during recovery😀 ________________________________________
2008 HSE RR Sport TDV8 Stornaway Grey

Glad your sorted, I thought it would be your problem! Get well soon and get the old girl running..  Current: 2010 RRS 3.6 TDV8 HSE
Past: 2012 4.4 TDV8 Vogue
2007 3.6 TDV8 Vogue
2005 3.0 TD6 Vogue
2007 D3 Commercial
2001 D2 4.0 V8 ES
1998 D1 3.9 V8 ES
1988 3.5 V8 EFI Vogue
Others: 2007 VW Touareg 3.0 V6
1998 Jeep Grand Cherokee 4.0
1990 Mitsubishi Shogun 2.6

Pop a message on the Disco4 side of this forum.. there's a few knowledgeable independents that maybe able to help you in your area. 2011 MY D4 HSE
Previously 2001 D2 TD5, 1996 D1 300Tdi, 1985 90 2.2 petrol.
Bikes! KTM, BMW, British, Classics and others.