Any one know what the pressure should be for the xf rail pressure? When at idle I'm sitting around 43-48 steady on graph and we'll driving it goes up to around 54 and stays steady.

 

The range is normally from around 500 psi at idle up to around 2100 psi under full power. It should be varying under different conditions.
Does your car have a problem? No units mentioned so not sure what your numbers mean?

Now I am talking about the HPFP and NOT the LPFP in the gas tank which runs under 65 psi and is the feed to the HPFP's mounted on the engine.
Always post all your car details so we know what you have. Year, engine, miles.
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Yes it is a 2009 XF and therefore likely a 4.2L engine in which case fuel rail pressure is much lower, around 320kpa.(I don't have the exact number).

 

My autel scanner has it in kpa and my innova was doing it in psi, not sure if there both reading same thing. Problem i had is i was sitting in car for about 45 minutes then i noticed the rpms dropped from from about 670 to under 500 and car started shaking. I was concerned it was misfiring but neaither of my scanners showed any historical missfire data nor were codes thrown now that being said i do have to p0193-00 code wich pops up intermittently.

 

And you are correct, 2009 premium luxury 4.2l non supercharged aj34s

 

Usually that code P0193 points to the FPR that is mounted on the fuel rail. Fairly cheap part and would be worth changing.
That might also explain the varying RPM's? It would be useful to monitor the fuel pressure when you see these variations.

Another example for the need to post full car details.
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it's in the shop now, rear diff seals were leaking so having new bearings and seals done. There going to check the sensor out as well.

 

One thing to check on the FPR? The rubber diaphragm often fails and then let's gas back into the vacuum line. Check the vacuum connection to the FPR to see if it's dry inside. If your going to replace it anyway don't bother but that is one known failure mode for this part.
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