No revs on startup

I have a 2001 Range Rover P38 2.5DHSE, the car has done just over 70k miles.

It has recently developed an annoying fault which my local LR garage is struggling to diagnose.

On startup when the engine is warm, the engine starts up and ticks over at about 500rpm. during this time there is no response from the accelerator, after about 10 secs the revs then rise to normal idle speed when power is then available.
The only fault recorded on the ecu is the fuel temp sensor.

On a cold start the engine fires up straight away without any struggle.

when driving the RR it feels like there is a loss of power since this fault occured.

just for info I had a superchip installed 4 years ago.


Thanks

Mark

sounds like a pump problem to me and being as the fuel temp sensor is in there you might aswell bite the bullet check for broken wires first though you should find a link to the rave disc somewhere on lz that will tell you were the wires are in the ecu dont get paying for the one on fleesebay its online for free you just have to find it good luck

is the engine burning well the fuel , as always ?