It sounds like the original problem is not the ECU; it usually isn't. P1621 is a common code. It's on both my cars, which run fine. You need to find the real cause of your problems. Try getting someone to looking at all the parameters in real time with a scan tool. Lambda sensors, cranks sensors and coils are the usual weak points on these cars, but throttle potentiometers can fail as well. Any members of the forum would need a much more detailed description of the symptoms to try and diagnose the problem.

 

Andy: I installed your bracket and the improvement was noticeable from the start. I have about 200 miles on the bracket and performance improved even more with time. Not sure why — but I’m VERY happy.
My experiences:
1) Gas-pedal responsiveness is greatly improved (delay is now undetectable)
2) The car maintains speed on uphill climb with barely the need to depress the pedal any further.
It’ll take a while to get an accurate measure of fuel economy but now that I am pressing pedal less I can’t imagine that it hasn’t improved as well. Only one problem, its more fun to drive now so I tend to press the pedal more.
You’ve made this car so much more enjoyable to drive. I wish I had your bracket years ago!

 

Andy,

I have a 95 XJR, Canadian Spec. I bought it cheap because it wasn't running well, and after talking to the mechanic who it was taken to, I found out that the owner had a dead battery and when attempting to jump start it connected the leads the wrong way around.

Do you think that reverse polarity would have fried the EPROM's? Finding a 95 XJR ECU is difficult here (only year without EGR) but XJ6 ECU's are not a problem to find.

I have computer tools to do throttle adaptation and lambda orientation if necessary.

I'm intending to do an engine swap into a Daimler DS420 limousine, so that was the purpose of buying the XJR. The XJR is badly rusted so I don't feel bad about scrapping it.

I have your bracket, is there anything else that you would do to improve low end torque in the Daimler? It's a heavy car so every bit helps. Would there be value in remapping the ECU? I'll be taking the entire driveline and fuel system components from the XJR and putting that into the Daimler.

 

The engine ECU hardware should be protected against damage from reverse polarity.


Fitting my bracket would provide most of the benefit that would be possible from re-mapping the ECU at a fraction of the cost. If you want even more torque from an XJR6 engine, then I would suggest fitting a larger crank pulley. This could provide a torque benefit equal to the % increase in the pulley diameter, which is limited to about 10%.

 

I would have thought so too. The symptoms was the car ran well for the most part, but occasionally the ECU would sense full load and fuel accordingly; then the car would flood and stall. The mechanic changed the ECU and AFM independently from a known good car he had in the shop and the problems continued. Owner ran out of money at that point and I bought it. I changed both AFM and ECU together and the problems went away.

It runs well now, but doesn't have the power I think it should, it feels no faster than a standard XJ6. I think the catalytic converters are plugged from all that extra fuel being dumped in when it was hot, so those are being replaced when I do the swap.

Thanks for the comments about the pulley, I'll look for one of those. Any ideas of sources?

 

Is the AFM you installed a known XJR model or is it for an XJ6? I switched my AFM's between my XJR and XJ6 and the XJR almost had no power and was using up a lot more gas (used up half a tank in 120 miles). I would double check that the AFM is the correct part number

 

I have just been through the process of hunting a new AFM (air flow meter) for an XJR.

be careful to get the right part - LNA1620AA (not LHE suffix - this is for N/A cars) - the XJR AFM is model-specific

And the really bad news, is - no new genuine ones are available (ie: Lucas). secondhand ones are out there on ebay, etc. New non-Lucas ones are available.
I have bought one of each, but can't report on how good they are - car still not going.

 

Yes, it's the XJR part. I knew of the different part numbers and I picked up two used XJR ones.

 

Okay I had my first one which was faulty reconditioned by these guys Fuel Injection Corporation
I then destroyed it using an oiled air filter which coated the hot-wire I then bought one from this company Jaguar X300, XJ6, XJS, Air Flow Meter LNA1620AA | World Car Parts > Store
It has worked faultlessly for 5 years and 40.000 kilometres cant say more than that as I sold the car January this year

Ran fine with all my mods and Andy's ECU remap what more can you ask for

Difference between the two it was cheaper to recondition but took longer to do with postage from Australia to the USA then back to Australia the other one no brand took 5 days fro the UK

I have bought a few air flow meters from world car parts UK no problems and very good price

 

So the XJ6 AFM is one of those that doesn't play well with oiled filters like a K&N?

 

I think so... I started having issues with my intake temperature reading right after I oiled my k&n filter...

 

I have resurrected this old thread, as the one about my bracket was getting a bit "off topic", and this one had a better title for what has been discussed recently.

 

I have been studying the XJR wiring diagrams today and noticed there is a road speed input to the ECU. How important is that to have?

I was planning to transplant this engine into the Daimler DS420 and was going to use the speed sensor off the transmission output shaft to drive the speedometer, with a suitable converter to change the frequency, and eliminate the need for the ABS system.

I can probably rig up the ABS ECU enough to give me a road speed signal, but wouldn't bother if that's something that isn't necessary.

 

Sounds like you need an Italian Tune up. If you get that cat hot enough it ought to burn off all that's clogging it up. Also Redex the fuel tank. It improved my XJ6 Sport 4.0. Probably worth burning a tank of fuel driving it mas power everywhere. Keep it in 2nd on Sport mode hehehe.

 

I believe the speed sensor on the Jag measures wheel speed. This means a change in Diff does not require re calibration of the speedo. However provided it produces the right number of pulses according to your speed on the road it matters little where the sensor is.

 

Dear Jagbio64,
I'm not entirely sure of all the software that may have used the vehicle speed input, as I stopped working on X300 nearly 22 years ago. From memory, this input was only used to disable closed loop idle speed control when the vehicle started moving. If you didn't have this input at all on your DS420 project I doubt you would notice the difference. If you wanted to feel the effect, you could temporarily back the vehicle speed input pin out of the harness connector to the engine ECU. The conditions when you might conceivably notice some effect on driveability is with the vehicle moving when the throttle is closed and the engine speed is below about 1200rpm. If the vehicle speed input is missing, then the other two criteria of closed throttle and low engine speed will be enough to trigger closed loop idle sped control. As your car is an XJR, and therefore presumably automatic, then under these conditions the torque converter will be unlocked, so I think you won't feel any driveline shunt. The service manuals contained on the Jaguar Heritage CD may define the nature of this signal and how it is sourced, if you want to replicate it. Reproducing this signal using some after-market product has been discussed at length on this forum in a separate post a few months ago.

 

That makes sense, thank you! I'm starting the process of stripdown of the XJR (yes, automatic) so once I get everything into the Daimler I will see what it's like. For a big car it has a surprisingly small engine bay, it will be a tight fit to get everything in. I know I have to make modifications to the transmission tunnel to get the rear of the transmission to fit.

I originally looked at a V12, but it's too wide.

 

Yes it does. My problem is the Daimler doesn't have ABS, so no sensors or tone rings on the axles to generate a signal. I's rather not have to figure out a way to retrofit that if I don't have to.

 

Hi,

I have recently purchased a1993 XJS Convertible 4.0L Six. Car needs paint a new top and seat covers, but otherwise is mechanically sound.

I was considering a V12, but the 4.0L Six was such a steal and considering the condition of everything and what actually needs to be done to bring it back to a looker, It became a no brainer. Car has 63K on it, and runs very nicely.

I have recently encountered a 1997 AJ16 Supercharged engine, Transmission and Computers for approximately 1000 total. I have access to tools, skills and facilities to get a mechanical swap done with no problem. My other car is a supercharged Mercedes SL55...I am considering making the move to upgrade my engine to the Supercharged Engine (Shocking!)...

My research has landed me on this thread, with the last update now about a year old.

I have studied E.E. an am not afraid of software or hardware.

Assuming that I get the mechanical swap done, Is there a list of things that I need to consider to make the Electrical and Software upgrade? Currently thinking of just swapping the ECU, but I believe the 1997 harness will have OBD2 and the car itself it OBD1, so I expect that there may be an issue to over come assuming all of the PID's and sensors would have changed in 4 years...Of course we are talking about two different vehicle programs as well... What am I up against!??!

 

The engine management system changed on the XJS changed at 94.75MY from Lucas 15CU to Lucas GEMS 6.2 with the introduction of the AJ16 engine. You will therefore need to interface the whole engine harness from the 1997MY supercharged engine into the XJS, as well as change the engine ECU. Although the GM Hydramatic 4L80E transmission that you have with your supercharged engine was fitted to V12 XJs cars, it was never fitted to the 6 cylinder XJS cars. This might create some harness compatibility issues when you try to fit the transmission harness from the XJR donor vehicle into the XJS. None of this is impossible if you have an electrical engineering background. I can offer documentation on all the critical electrical connection o n the engine harness that need to be connected for an AJ16 engine transplant, such as you are planning. Please email me directly if you want to discuss it. Mechanically speaking, you will need to install electric cooling fans, as the AJ16 engines in X300s did not use viscous cooling fans, unlike the XJS. You might need a special propshaft because I assume you will be replacing the ZF 4HP 24E transmission with a GM hydramatic 4L80E. Alternatively, you could retain the ZF gearbox, though it is only rated to 466Nm torque against the AJ SC engine output of 512Nm. Mechanically and electrically , it would make the installation simpler to retain the ZF gearbox. The 93MY ZF gearbox ECU won't interface correctly with the 97MY engine ECU. The gearbox should change gears OK but the engine ECU may go into a reduced performance mode. This can be offset by fitting one of my revised crank senor brackets to advance the ignition timing by 5 degrees. Good luck with your project.