In addition to adding Heat (alcohol) and injector cleaner to the fuel and swapping MAF and coils, now I swapped crank position sensor and fuel pressure regulator. All of which still resulted in missing, lumpy idle and low rpm's while stopping and then intermittent stalling.

I then swapped out the throttle body complete with throttle position sensor and idle control valve.

Now:
Cold starts - car idles at 1700 rpm and after warms up idles at 1100.
Warm starts - car misses and car tries to idle at 500 rpm and dies. I must give the car gas to keep from stalling. This condition lasts for only 20-30 seconds then car will smooth out and idle at 1100, and is driveable.

It's acting like it needs an ECU orientation, as I've had a mechanic do this for this car once before due to this same high idle, but the stalling at 500 rpm on warm start makes me think the initial problem may still exist but is masked by the high idle once the 20-30 seconds passes.

Still not happy...

 

As you have replaced the TPS, you will need re-orientation of the ECU. If this does not fix your problem, and if temperature makes a difference to engine response, you may have a bad engine and/or coolant temperature sensor.

 

In my opinion if you read the wire and is in range on the 0.60 + or - 0.02 volts you may not need a reorientation with the cost involved and appointment hassles . You can read this value with the key on and engine off by tapping into the return (Green / Yellow wire ) to the ECU wire as it goes over the top of the engine . This would also depend on how the present orientation setting or matching is with respect to the previous TPS . Note that the factory holes of the sensor may not be placed to be able to put it on the factory recommended range and I had to drill them up in size in order to do so . If you have enough patience the sensor mounting screws can be got to from the top without removing the TB .

With respect to the engine coolant sensor it's one of those oh by the way this is also involved thing overlooked and forgotten . As the coolant temp is low it biases the fuel trim or mixture to the rich side until the engine warms up . This could be making the idle high . It's an exposed connector so I would look at it and clean it up and preserve it . You can easily remove it and calibrate it's accuracy by dipping it in ice water and boiling water and verify the results on the graph . It's a negative temperature coefficient (NTC) thermistor so the response is opposite from the old school plain resistor style . This is the same response chart of the inlet air temp sensor just forward of the TB on top of the 90 degree turn . If you don't already have this full doc that it came from , here it is below :

http://www.jagrepair.com/images/Trai...20-%202000.pdf

 

Having taken a quick read through here, my 97 X300 had a similar issue until one day it refused to start again and I had to have her towed to a shop, turns out it was the crank positioning censor, it was replaced for like $400 and then never gave me any more grief, I don’t think anyone’s mentioned that yet but I apologise if I’m repeating information. Hope maybe this helps man.

 

Good point , as they fail from my understanding it will give issues without codes as the crankshaft position sensor signal controls spark and injection timing , Fuel injector pulse width or trim or mixture , and fuel pump shutdown and others I don't know

They are about $ 125 dollars at the local part store and are easy to change with no adjustments , Jaguar # LHE1640AA , Duralast # SU4719

You did have a code P0727 , and a spare in the trunk wouldn't hurt

 

another symptom I forgot to mention is that it would go into “limp home mode” after restarting or dropping in revs so perhaps if they also get that (I don’t believe they mentioned it) then there’d be a decent chance the crank position sensor is the culprit

 

CPS was mentioned in Post #12, and RFXJ12 said in #21 that he changed it but problem persisted.

 

Without focusing on the CKPS and saying that that is the magic bullet although it may be, there is the possibility that the new part is bad out of stock . See if you can get another one with the agreement beforehand that you can return it , not always possible with an electric part . I've delt with bad parts more than I would like to while passengers look at me and I mean all 125 of them at once . Inspect , clean , and preserve the connector and the wires as it runs up the front of the engine in an exposed environment .