Well, I assume that the original module has something amiss or you would not be trying to change it, so it would make sense to go ahead and do the deeds on them both while yiou were there.

 

I''ve been having weird issues with my original ecu after I tried installing it into a regular XJ6. First it was the extremely high idle (1800rpm in P/N) and slight hesitation. I tried taking it to a shop but they told me they needed to clean the intake and replace the IACV but I knew it was just something having to do with my ECU so I didn't have them do it. Eventually for the past year or so I've just had the IACV unplugged and let the TPS control the idle which brought it down to 700-900rpm at idle depending on how it felt that day. I dealt with it until I got my hands on another ECU for an XJR and that is when I confirmed that the IACV was working as it should since this second ECU set the idle at the correct 650rpm at idle.

I plan on taking the car into the shop tomorrow morning and having them do the new engine setup with the new ecu I picked up. I'll ask if they can do it for my original ecu also.
Should I ask them to do the original ecu first or the new one first? Would that even matter?

 

I would say it did not matter.-
I have an explanation for the situation on your original ECU. Years ago, at least on the JL forum, there were reports of ECUs that would lock up the fuel trims when operated for a long time with the O2 sensors swapped. It was reported, as I recall, that the ONLY way to get the locked up ECU working again was to do the re-orientation.
Now, to your situation. Remember, the physical connection of the lambda sensors for the two banks are arbitrary and front or back banks can be swapped between cars, with the ECU "knowing" which is which via the orientation. So, assuming the wiring on the other car was oriented "backwards" from yours, and assuming the old stories of the ECU locking up when the sensors were backward- then that would explain how your original ECU got fouled.

I would get both modules oriented (and TPS calibration) while you were there. Booting up the machine, making the connections, and remembering how to do the procedures take more time than pushing the button and doing the function. Of course, since the procedure is done in the car with the engine running, if you have the panel open and the bracket loose, it will take less time to swap ECUs. He should give you a deal on a "twofer".

Good luck and let us know how it turns out.

 

Quick little update about the car and my luck...

took my car to an independent jaguar shop to get the O2 sensor orientation and TPS calibration done. After some confusion about the front desk guy thinking I wanted an ECU reflash and relaying that to their Jag tech, I told him what was going on and I had to specify that I wanted an o2 sensor orientation and TPS calibration done. This is a Jaguar/Ford Diesel shop so I guess I got lucky that they had the old Jaguar PDU's. There was some confusion as to what my ECU was (Jaguar or Ford made). 1997 XK8's I guess were Ford made already so their front desk person assumed I had a Ford made car. But couldn't really complain since they didn't even charge me for anything.

I was going to ask them to do both modules if they were going to charge me but since they didn't I decided not to ask.

Anyways, after I picked up the car, my rough idle was gone, and my STFT looked like it was behaving as it should... NOW here's the best part..

I only got literally 2 stop lights away and I started leaking coolant everywhere. Just my luck, my hose going from the water pump to the water rail burst. In the back of my mind I keep thinking that the shop had something to do with it but I'll just assume that it was the hoses time.
I haven't gotten the intake manifold off yet (only have the injectors and intake off) but I'll see what the hose looks like and see if it was tampered with.

I was just about to start enjoying my correct idle speed and no misfires but only got to enjoy it for about half a mile

 

There is nothing near that hose they would have touched. They did need to idle the car for a while, so it might have pushed a failing hose. i believe the one you are referring to is the bypass hose more commonly known as the Bast*rd hose on an X-300.

 

That's why I'm thinking it's just a coincidence that the hose failed right afterwards. From what I can see so far, it looks like a hose tear... I'll take a picture once I get the hose removed...
But yes, I was dreading this job but now I guess I have to do it. It's a chance to clean my throttle body and intake which I haven't done since I bought the car over a year ago. It's just amazing how after I fix one issue with the XJR, another one pops up right after and with my XJ6, that car has been issue free since I bought it, 3 years ago..... *knocks on wood*

It's true what they say, having a boosted car is a bigger headache than an N/A car.

 

Here's a little update regarding the car and misfire issue:
Replaced that damn water pump to water rail hose over the weekend. I don't understand why they had to make it a rubber hose and not just a pipe from the water pump to the water rail... I mean it's only like 6 inches? I took a short cut and only moved the intake manifold/intercooler assembly off to the side to reach the hose.

As far as my misfires and fuel trims go... everything is running as it should. My LTFT was at 0.00 at one point which I've never seen before. I read that if it reads at 0.00 the ECU and o2 sensors are doing exactly what theyre supposed to do. But during my commute to work this morning, I was getting -6.12. Oh well. I'm happy and the TPS calibration and o2 sensor orientation worked.

 

I have not heard of a "locked up" ECU in many years and I never really had proof that mine had done that, although there were indications. I see no other explanation for your circumstances, though.