Losing power

My 2005 Jaguar X-TYPE 2.0 V6 has 180,000 kilometres on the clock and has recently started losing power when driving. This is so bad that it has got to the point where it switches off if I keep on trying to accelerate. When I turn it on again, it starts up and gives me a bit of distance before switching off again.

I was advised to change the fuel filter, after which there was a slight improvement before the problem came back again. Now I’ve been told to get a new fuel pump. What do you think?

You have not mentioned if the engine management light has been illuminating. If it has, this may help pinpoint the problem as it would leave a code in the system. With the benefit of a fault code, diagnosis would be easier.

As there was a slight improvement after replacing the fuel filter, this suggests that the problem may be related to fuel shortage. It would have been interesting to know if the old filter was contaminated when it was replaced, which might indicate a problem with the fuel. Any contamination of the fuel could damage both the fuel pump and the injector system.

As turning off the engine and turning it on again does improve matters, this strongly suggests the fault is electrical, which is being reset after turning off and on again. If this is the case, a fault code should be retained in the system and, if you have access to a code reader, may help highlight the problem.

Other possibilities that could affect the power output is a problem with the fuel pressure regulator, which is vacuum-operated on your Jaguar, or that the fuel tank breather system is blocked or that the evaporative emission (EVAP) canister purge valve is stuck closed. This would have the result of causing a vacuum in the fuel tank, which is preventing the petrol from being drawn from the fuel tank, resulting in loss of power and engine shutdown.