Now I know the V8 disco is not a ball of fire but I am concerned all the power is somehow ebbing away as it seems to struggle to keep up with traffic. The engine runs fine and sounds great, fuel consumption is steady at 11mpg (terrible I know but only used around town) Plugs and leads have been changed and it will eventually hit 80-90mph and stay there all day but lacks acceleration. The car has done nearly 100k miles and is in great condition. One thing I noticed is after unplugging the MAF the car ran exactly the same, would this point to the MAF being defunct and the car running on baseline trims, there are no engine management lights on.
I've heard that camshaft wear can be a factor in blunting the performance, is there any way of checking this without extracting the camshaft?
Any ideas much appreciated.

I'm not sure you can really claim it runs fine, but power is ebbing away. They would seem mutually exclusive to me.

What V8 is it? 3.5's and early 3.9's should go well enough, the latter more so. Although will feel like they need winding out, rather than being free revving.

Latter 3.9's with the Serp belt and electronically controlled gearbox or 4.0/4.6's should feel rather peppy and free revving. More so than the older ones.

None should be sluggish really. So sounds like you have a few things going on.

11mpg also sounds terrible. Never had such low mpg from any V8, think even my V12 Jag did better. For the record my current 4.6 used for short journeys, hooning about and a bit of off roading is going 16.9mpg pretty constantly.

Older V8's such as a RRC or Disco 1 should still be 15mpg+ really unless you have a very heavy right foot and journeys measured more in yards than metres.

Worn cam and followers is common on RV8's. But you might have something electrical going on too or even something else.

A 3.5 V8 or early 3.9 D2?.
Anyway with a 100k miles on the clock I would think a full top end overhaul is now in order, then u can check for engine wear.
My old RR 3.5 had the have a cam replacement at 100k miles so it's not unheard of.
As far as V8 fuel consumption goes I never checked my 3.5 TVR but my RR 3.5 did 16 mpg everywhere through out the 10 years I owned it, now my 3.9 disco is 18 to 22 the last time I checked a couple of years ago much as I would expect in all the 19 years of ownership.

Modern V8 cars are a lot better Ive had 37mpg from a 4.2 and that's real time from the dash desplay at 60mph, but it dropped very quickly when the pedal was to the metal

Missed the D2 tag, only read the title and the op

100K is as the others say the poin t where wear BEC ones a real issue in the cam, followers ect. Not an expensive job to do

discool said:

As far as V8 fuel consumption goes I never checked my 3.5 TVR

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senior moment?
I did drive my TVR like a TVR and that did an average 20mpg sold it when I got a 3.5 RRC that did and average16mpg every where. The last time I checked my 3.9 it was around 18mpg average.

spitfire said:

would this point to the MAF being defunct

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Sounds likely. How long does it take to 60mph?

Hi and thanks for the replies. It is the later 4.0 engine (Thor) and really runs great. The engine revs freely with no misfire but under load just doesn't seem to want to go. If I whip the cam covers off and check the lift any idea what kind of movement I should see on a decent cam?
I must agree the 11mpg is hopeless, it will go up to 17 or so on a run. My 4.2 Supercharged Range Rover gives me 24mpg and that's got 400bhp so I guess there must be something wrong.