First and foremost, I tune and mod Subaru's. The XKR in question belongs to my dad and I have next to zero Jaguar specific knowledge, even though the ecu and electronics systems looks extremely similar to the Subaru's from around year 2005ish, so bear with me here.

So the car died of a oil starvation caused by a ruptured oil cooler while going over a railway about half a decade ago. The old man was on the phone (I know, sheesh) and didn't notice the oil lamp coming on, kept driving, and the engine died. I was living in Nottingham at the time so I simply drove up to Auto Reserve Ilkeston to pick a used AJ27S for him. 133k miles on the clock but was said to be free of issues.

Handed the engine over to him, and apparently his mechanic literally chucked the long engine in without touching a single thing (no even the seals and other consumables, good riddance, it's still leaking from the main seal as of right now). Ever since then he's complained to me that the car didn't feel as fast as it was (the dead engine only had 30k miles on it).

Fast forward to today, I decided to have a close look at the issue, and I was shocked. MAF showed only around 225g/s at red line in 4th (which should roughly translate to 270ish bhp), and a no launch 0-100km test done with P-Gear gave a result of 7.44 seconds. A full 2 seconds away from the claimed 5.4. lastly, anecdotally, this thing feels so much slower than my 300bhp Scooby, and it definitely shouldn't be.

Now for the questions:

1. Is there any way to datalog the car properly? I was able to read the datastream from my Launch OBD reader bit the data available and the resolution is definitely not up to scratch. From what I can tell the car is running off of a Denso SH 705X based ECU so theoretically my Tactrix cable should be able to log data from it once I sort the definitions out? If I am able to see what the VVT valves and O2 sensors are doing it should be really easy to see what the problem is.

2. What's the compression like on a healthy engine? I'm highly suspecting it's the piston rings thats on their way out since there really isn't that many things in an engine that can lose you 100+ bhp. So a compression test is definitely on the cards.

3. What's the boost pressure supposed to be for an untouched engine?

Thanks in advance.

 

Forgot to add. The car drives fine. Idle is perfect too, so I've preemptively ruled timing and ignition related issues out. Obviously if that's not the case, feel free to correct me on it. Thanks.

 

Sounds like the #2 fuel pump is not kicking in when the power demand is high likes it’s supposed to do.

easy to diagnose by pulling the fuse or relay for the #1 fuel pump. If the car won’t start after repeated attempts, then the #2 pump is dead.


Z

PS you need the shop manual to answer
many of your questions. Look for the 1999 shop manual in the “sticky topic” section. You
can download it after a few postings.

PPS the 4.0 XKR’s don’t have the VVT you mentioned. Only the XK8’s have it.

 

For an AJ27, I think boost should be around 12 psi or so.
AJ27 ECU is Denso, I believe similar to Subaru, but is earlier, so not Renesas but Motorola/Freescale 68HC16, so you still might be able to get somewhere with the Tactrix gear - I think the early 2000s Subarus used Denso/HC16?
You can log O2 upstream which are wideband using the JLR IDS software+adaptor, or you could trigger CANbus output of O2 current using PIDs - see documentation from postings by crbass for codes, or maybe your Subaru adaptors can do that.
+1 on checking fuel pressure/dead fuel pump - ECU will adapt to using whichever of the 2 pumps is still working, so stealthy issue, per zray the second pump only activated at higher revs (3000+?) when needed.

 

That is extremely helpful. Thank you so much. Will get around to testing it tomorrow.

One thing though, wouldnt something current based like a fuel pump going out trigger a CEL? Or does the ecu not care about it?

Thank you. Will log manifold pressure on the obd reader tomorrow to see whats what.

Yes earlier Subarus (Pre-05 Imprezas and by extention, the Foresters) are HC16s. This Jag ECU looks more like a later 32bit Denso thats semi CAN based. Iirc a buddy of mine that fixes dash clusters has mentioned that the mid 00's Subaru's cluster is extremely similar to older Jag stuff too.

​​​​​​​

 

I think that era AJ27 will have a PCM (ECM) with twin SH7052 CPUs.

See JagRepair.com - Jaguar Repair Information Resource

e.g.

881 Manual-9-5-01.pdf (called Jaguar V6 / V8 Engine Management #881)

(If all else fails, open the PCM box and stare at the chips LOL.)

I can't find where TINTR02-VIN-decoder.pdf lives but it also refers to 2 CPUs in the PCM (ECM).

 

On page 5 of the "The XK8 Engine Management System And Electronic Engine Control Module" (available on jagwrangler site) - The ECM consists of two 16 bit Motorola 68HC16 microprocessors.....
This description is for AJ26, but AJ27 is an evolution of the AJ27 ("increased processing power and memory capacity") - processors on the PCB are labelled Denso 151851-3830, which as best I can figure out are actually Motorola/Freescale/NXP 68HC916Y5 devices (160 kByte flash), also both have a 10pin BDM interface which is hallmark of Motorola. I believe same chip used by Denso on 2001-2005 WRX.

 

On boost pressure, I may be wrong here so recommend you check, but I think the MAP sensor (if you have one fitted - some AJ27 XKRs don't have them) is only used to detect vacuum to validate EGR valve is operating, and so won't give you a decent reading of boost over OBD2. If so, you will have to fit an aftermarket sensor - you can tap into the pipe between the supercharger and fuel pressure regulator - plenty of threads on that.

 

If interested I would definitely be looking at the PCB inside the PCM's box.

 

Something that can affect XKR performance is failure of the intercooler water pump. If it fails, it will simply stop and not throw a code. The cooling water circuit will cease and render a major engine system useless. The compressed air will enter the cylinders at about 12psi but ‘uncooled’ and approx 135 degrees C (instead of the normal 80 degrees C). This will reduce torque considerably – more than 50 ft/lbs at 5000rpm and would definitely be noticeable.

The pump is located under the Air Filter but there is a very simple method of checking that it is working.

1. Engine off.

2. Turn on ignition (Key position 2). Engine is not running.

3. Listen for the pump running – located under air filter. It is one of the few things running under the hood.

4. Squeeze pipe with fingers (where shown) to restrict the water flow.

5. If you hear the pump change in sound as it struggles, then all is OK. There is coolant and there is flow.

6. If you can’t hear the pump or there is no change in sound, then investigate Pump / Fuse / Coolant.

 

My 2000 XKR with 100k miles on it has 11 psi of boost pressure.
And the compression pressure is around 160 psi, tested with engine at operating temperature and WOT.
These engines (up to autumn 2000) has Nikasil cylinder bores and therefor the compression test would be my first priority.
Second, check the valve timing.
I assume you have checked it for vacuum leaks? If you have leaks the MAF would read to low.

 

can you tell me where you are measuring the boost pressure ? A stand alone gauge, or …. ?

If a gauge, what brand and where is it hooked up,

I'm always interested in what my engine is up to; performance and general data too. I’d have more gauges than a Boeing 747 if there was a way…..

Z

PS from period road tests I’m told the XKR’s (4.0’s) have less boost than their Ford counterpart of the day, the Ford Lightning pickup, which used the same supercharger, but different sized pulleys .