Thread: Loss of power when warm?

Changed the fuel filter this morning (old one was very fould up). Took her for a test drive, but doesn't seem to have fixed it, put my foot right down and started loosing power. The more throttle I gave the worse it got. Even less power if I push sport mode. Although smaller amounts of throttle it seemed ok.

If the crank position sensor is faulty then surely the engine should exhibit problems as soon as you try and start it...?

Secondly, since it seems OK for an hour or so when starting from "cold" then progressively loses power...am wondering about a temperature-related issue...

There is a fuel temperature sensor which is critical to proper functioning of the fuel injection system... there is also a fuel pressure regulator.... I suggest you get these checked...

I'm thinking fuel starvation ...

Have you tried bee utey's suggestion re loosening the fuel cap?

EDIT: another thought: how long is it since you have checked out the relays ( in the fusebox beside the battery) esp. the one controlling the fuel pump... look for brown burn marks on the yellow ones especially...

Thanks for the reply hoges, she starts up fine and even if it stalls after power loss it's starts again after a minute no problem. I did try the fuel cap, but no change. I did look at the relays a few weeks ago as I needed to change the relay for the a/c and I do remember the fuel pump reply having some burn marks on it, but as the pump was working I didn't think much of it.

Another update, swapped the fuel pump relaywith one of the good ones and went around the block. Still no change, drives ok at low to medium throttle but when I put my foot down she looses rev's/power for a few seconds the kicks back in for a second then looses power again and so on.

Did you try the cold water on the CPS trick yet? I must admit I have never tried it on a p38 Range Rover however on my Merc its the first test when loss of power or stalling symptoms occur.
The CPS goes bad when hot so cooling it gets it working again.
It could also be the Maf sensor. You can clean the Maf but I doubt a dirty maf would cause your Symptoms. A new Maf can be had for less than $60 on e-bay and wouldnot be a bad thing to change anyway if its the original. search for part 0280 218 010 . I would try and find someone close by who was willing to put their maf into your car for a quick test. Its only two screws if you have the right screw head bit. ( I always change mine to std cross head as I clean mine every 6 months)
Have you tried a generic OBD2 reader to see if there are any clues?

Originally Posted by wayneg

Did you try the cold water on the CPS trick yet? I must admit I have never tried it on a p38 Range Rover however on my Merc its the first test when loss of power or stalling symptoms occur.
The CPS goes bad when hot so cooling it gets it working again.
It could also be the Maf sensor.
Have you tried a generic OBD2 reader to see if there are any clues?

Haven't tryed the cold water yet, still having trouble locating the CPS, although when I put my foot down in it today it was right after pulling out of the drive way so the car wasn't hot yet, but still had power loss. (only when giving a lot of throttle.) I have plugged the OBD scanner in and she's not Showing any fault codes. Idid clean the MAF sensor at te last service a couple of months ago while changing the air filter.

Can you borrow a fuel pressure guage to see what's happening under load?

I wonder if the fuel pressure regulator is weak...disconnect the vac hose or clamp off the return hose.

Originally Posted by Scouse

Can you borrow a fuel pressure guage to see what's happening under load?

I wonder if the fuel pressure regulator is weak...disconnect the vac hose or clamp off the return hose.

Thanks Scouse, my mechanic did test fuel pressures when I took it in to him and he says they are fine.