The EGR valve on a Jaguar recirculates the exhaust gases from the manifold back into the engine for a better burning of the spent fuel. When this valve is dirty, you may notice an extremely rough idle below 800 RPM. You can clean the valve once you remove it, rather than replacing it, which is much more expensive. Once the valve is cleaned of all carbon deposits, it should work like new.
Fill the EGR valve opening with carbon cleaner. Fill up the valve until the cleaner comes out of the top of the valve opening.
Let the valve soak in carbon cleaner for at least eight hours. This will loosen the carbon built up on the inside of the valve.
Dump the carbon cleaner out into a container approved for solvents.
Finish cleaning the rest of the carbon out of the valve with a wire brush. Most of the carbon should come off rather easily at this point
Wipe the valve with a shop rag and allow the inside of the valve to air dry.
For specific information about your Jaguar's EGR valve, consult the particular vehicle's manual (see Resources).