Hello Men,
My 2001 XKR runs steady a steady 38 to 40 psi fuel pressure from 20 inches of mercury vacuum up to zero vacuum. When manifold pressure increases from 0 to 15 psi, the fuel pressure increase to 60 psi.
The problem is that the car stumbles under Wide Open Throttle, but occasionally accelerates fine under WOT. When the stumbling occurs, the fuel pressure needle chatters between 45 and 60 psi, when the car accelerates strong the same gage shows a steady 60 psi.
The car holds 35 psi fuel pressure after the engine is shut off. I'm not certain if the stumbling with chattering fuel pressure is a pump issue or pressure regulator problem. No check engine codes appear.
I just purchased a NCA 3007CA fuel pressure regulator on ebay for this 2001 XKR and the pipe is different than what appears to be original on the car. What is confusing to me, is that the parts supplier lists the same regulator for the XK8 motor as the XKR.
Not sure how to proceed here...
Thank you,
Mike

 

It may be the fuel pump or fuel filter.

 

Hi Mike,

I have moved your post from the forum for the X308 to the forum for the X100, which is the Jaguar factory project code for your 2001 XKR. Here you will find knowledgeable owners of similar cars who may be able to help.

I agree with RJ237 that the fuel filter is a good start. At first glance, your fuel pressure readings while running and after shut-off don't seem to indicate a problem with either the fuel pump or FPR (although 60 psi may be on the high side - I'm not sure of the spec for the XKR).

Off the top of my head, some other possible contributors could be:

1. Contaminated or poor quality fuel or octane rating too low
2. Air filter
3. Throttle cable out of adjustment (adjust to eliminate slack from stretching)
4. Spark plugs fouled or gaps too large due to electrode erosion
5. Failing ignition coil(s) (remove the covers and watch the engine run in the dark for signs of arcing - failing coils have been known to cause problems without triggering fault codes)
6. Oil in spark plug wells due to failed cam cover gaskets causing arcing or leaking down plug threads and interfering with plug ground path
7. Failing ignition coil relay
8. Partially plugged fuel injector(s) or failing fuel injection relay
9. Engine Coolant Temperature Sensor failing (causing improper fueling enrichment)
10. Corrosion on electrical connectors and/or ground studs critical to the Engine Management System (EMS), causing the Engine Control Module (ECM) to receive altered sensor readings
11. Failing or contaminated Throttle Position Sensor(s) or electrical connector to the TPS and throttle motor
12. Contaminated Mass Air Flow Sensor (MAFS) - try cleaning it with appropriate zero-residue spray
12. Intake plumbing air leak between MAFS and intake manifold gasket (this will usually trigger a code)


Some of the above may be way off the mark, but most aren't too difficult to check. Hopefully some of our XKR owners will have better ideas.

Cheers,

Don

 

the 01 xkr has 2 fuel pumps which the secondary kicks in under hard acceleration or WOT, Do a search or check diy sticky there is a test for the fuel pumps, you've probably have one dead or if ur lucky a fuse/relay

 

Hi Don,
Yes, I may have been too hasty to replace the FPR, given the other possibilities. New fuel pumps were installed prior to me purchasing the car, and the first thing I replaced was the fuel filter. I have jumpered both fuel pump relays to verify that both pumps work, but not yet verified fuel pressure while sustaining a measured volume of flow.
I should probably investigate the other possibilities you suggested before I further damage the OEM fuel pipe trying to make the new NCA3007CA fuel pipe with FPR work. (Don't know why the NCA3007CA did not come with the same fuel pipe as original to my car, but the DENSO number on the FPR does match)
I just replaced the cylinder heads 1500 miles ago, so I may have been over confident not checking the ignition performance. I'm kind of perplexed that the car runs smooth and normal until manifold pressure climbs to 15 PSI. The car stumbles until it reaches 5000 rpm, then the fuel pressure stops chattering and stabilizes at 60 psi, and then engine runs strong upto the next shift point near 6000 rpm.
I should probably post a video of the manifold pressure and fuel pressure during the acceleration cycle.

 

If it is a failing pump, and you are lucky, it will hesitate under WOT before it dies (unlike mine did).

 

The original 2001 XKR problem seems to be multiple misfires under wide open throttle, with dark smoke coming from the exhaust during WOT.
I changed the plugs to an autolite #3924 gapped at 0.040 inches and this problem was totally resolved for about 1000 miles (the more expensive double or single tip iridium plugs didn't help).
But now the WOT stumbling has come back again.
This multiple misfire occurs after the engine is warmed up. It stumbles under WOT up until 5000 rpms, then all cylinders fire and it runs strong up to the 6000 rpm shift point. My mechanical gauges measured the Fuel pressure to be 59 psi when the manifold is at 15 psi boost. Never has there been a Check Engine Light or any OB2 Fault Codes during or after the WOT stumbling.
Since the issue is sensitive to spark plug types and gaps, I am inclined to believe that the factory ignition coils are of marginal capacity.

My 1999 XJR has always run flawlessly, 12:90 at 108 mph. The coils do not appear to be interchangeable between the 1999 XJR and the 2001 XKR.
Does anyone know of an upgraded ignition coil alternative for the 2001 XKR? Accell does not offer anything.
Is there any data to support that one brand of coil is superior to another for the 2001 XKR application?
Thank you,
Mike

 

Can I suggest you clean or even better change the MAF. Dead easy job.

Here is a simple test for you to do. When the car is moving see if you can get the revs up to 5,000. Let me know how you get on.

 

I would say, besides fuel pressure, check the manifold pressure, too. Maybe the absolute fuel pressure drops because the intake pressure drops, too (you are not maintaining the boost pressure somehow). It is probably hard to tell, but are there any signs/sounds of air leaks? There are some issues with supercharger seals on the early cars, seals that have been redesigned at a later point. I believe there is a TSB (check jagrepair.com). XK8 here, so not direct experience...

Besides that, 5000rpm is probably near maximum torque, so check your engine mounts for excessive movement. Maybe the engine rocks so much some air leaks develops at max torque.

Last, just to throw it out there, is it possible the throttle is backed off because you are loosing traction? I am unsure what system came with the 2001MY (ABS and/or TRAC).

 

Check the function of the vacuum operated supercharger bypass. This could cause your problem.

 

The important word here was try to get to 5000 rpm. You cannot do it at a standstill as the limiter kicks in, you will just get a bouncing rev counter. Try it and you will see what I mean. You do not have to be going fast. Using the J gate go up a steep hill in 2 and you will soon get it there, if it can get there that is.

 

For who can and wants to help,
I wish this tread would have proceeded and had come to a proven solution back in 2018.
This because I have exact similar problem and have tried pretty much anything so far.
Some time ago I bought the car with this problem (and some more) so can't do Is and Is not analysis to find causes, can just check some facts and eliminate. (but analysis paralyses kicked in many times:-))

The problem is that the car stumbles under Wide Open Throttle, but occasionally accelerates fine (better) under WOT. (Engine hotter is worse, when cold seems better but I never push a car when cold as I have blown too many already)
My 2000 XKR runs a steady 38 to 40 psi fuel pressure when on pump 1. When I put some pressure on manifold line to fuel pressure regulator and increases from 0 to 12 psi, the fuel pressure increase to 50 psi (with pump 2 also jumpered by a lead from battery)
I have checked charger coolant temp and it seems to be actually cooling the inlet air. (When engine 88C coolant--> intercoolers are ~35C)
When this cluttering during acceleration happens the ignition timing advance is removed by ECU, and Short term fuel trims jumpt for far in the +% to 0,0%.
When just stumping the pedal to the metal, at higher RMP the engine picks up somewhat better (also by kink down- shift RPM shoots up obviously) but this feel like destroying the engine a but (as it might run way too lean and drive valve seat or something...)

I am now planning to remove 10% pulley upgrade to fix the problem...(My ECU is still stock, and is is said this cannot work)

I've changed coils, plugs, Maf, Crank sensor, Conductor plate.
Valve timing is good, engine runs very smooth idle and also revs fine when in neutral (some knock from drive rod when cold - 1-2 miles)
Car drives fine as long as I do just some slow city driving, or take time to get to highway speed:-(..
1. Contaminated or poor quality fuel or octane rating too low
2. Air filter
3. Throttle cable out of adjustment (adjust to eliminate slack from stretching)
4. Spark plugs fouled or gaps too large due to electrode erosion
5. Failing ignition coil(s) (remove the covers and watch the engine run in the dark for signs of arcing - failing coils have been known to cause problems without triggering fault codes)
6. Oil in spark plug wells due to failed cam cover gaskets causing arcing or leaking down plug threads and interfering with plug ground path
7. Failing ignition coil relay
8. Partially plugged fuel injector(s) or failing fuel injection relay
9. Engine Coolant Temperature Sensor failing (causing improper fueling enrichment)
10. Corrosion on electrical connectors and/or ground studs critical to the Engine Management System (EMS), causing the Engine Control Module (ECM) to receive altered sensor readings
11. Failing or contaminated Throttle Position Sensor(s) or electrical connector to the TPS and throttle motor
12. Contaminated Mass Air Flow Sensor (MAFS) - try cleaning it with appropriate zero-residue spray
12. Intake plumbing air leak between MAFS and intake manifold gasket (this will usually trigger a code)

After trying so much options, and work before me to change the charger, I would like to have confirmed that the reverting back to a standard pulley is known to solve these problems entirely.
It seems detonation is currently triggering the knock sensors, ending the fun each time throttle is opened a little faster.
But why?
Or is TRAC even working when switched of and is there some traction sensing problem? ( I have the ACC and Trac option)
The car throws NO CODES whatsoever..
Apart from that I suspect the Cat-converters to be on the way out (one is missing some honeycomb material after the downstream lambda sensor)), but could this be related?
Rear subframe and Diff have some play here and there..
Related?

Any ideas?
Would be very much appreciated!

Thank, Rob

 

I had similar problem in that it would not go above 3000 rev when moving. Normally this only occurs when your standing still. The rev 'bounces' and will not allow you to get WOT. Will see if I can find a video clip for you.

This is what I am on about https://www.jaguarforum.com/showthre...=1#post1074265

 

I went down the same road with my 2002 XKR. I suspected that the ignition system did not have the capacity to fire across a large Platinum or or Iridium spark plug gap with the turbulence in the combustion chamber under WOT. Decreasing the spark plug gap to 0.035 inches cured the problem. I also switched to conventional Autolite spark plugs. Still run an oversize pulley on the harmonic balancer. Runs like a raped ape!

 

Thanks Mike,
Mine has the 0,9mm gap plug already.
Will source other ones just to be sure.

For clarity, mine can get to high revs, but gradually, or faster with lot of cluttering.

I have found somewhere that inlet temp in the coolers is (also) used as direct relation by ECU to retard ignition (when high temp).
Charge air temp itself is fine although measured wit IR temp reader because my ELM can't show that value(!) . At least it doesn't....maybe it could and ECU does not provide it?
Sensor seems fine. (resistance between 1.4 ohm when heated, 3,5 ohm when cooled on the bench.
But there could be an ECU problem?

Can anyone else see a CACT value (charge air temp, from the actual cooler sensor on the OBD2?) on an 2000XKR? (so not the inlet temp from MAF temp sensor)

Thanks for helping:-)

 

NOTHING good will come out of a broken converter. I had a car once that worked fine, except when it did not, and the power output dropped dramatically. Ended up being loose pieces of honeycomb material would sometimes work their way out of alignment with the main flow and create massive back pressure. No air out means no air in, so air flow meter measured less, less fuel, everything seemed "perfect", no codes. Test was to gut out the cat and rediscover what the original car felt like. This would seem to mesh with your knock scenario.

Best of luck, keep us posted.

 

No codes tells me the stumbling is likely not misfire/ignition related.

Are the fuel pressure reading under WOT when the stumbling is happening? My first thought when I read your post was failing fuel pump. They can sometimes have good pressure but cannot produce enough flow volume. The XKR has two.

As noted above, a cat can fail and block the exhaust just enough so it runs ok at low load but not at WOT.

I had something on my throttle body go bad, not your exact symptoms, but it messed up the mixture which could cause loss of power also.

 

Thanks!,

Pressure was not measured under WOT but by jumper lead to both pumps and air pressure source on the regulator to simulate boost. (As I suspected the regulator to not raise pressure under boost)
Is 50 PSI max normal/enough? or should it be 60 PSI?
Before, when I was replacing the fuel filter, I checked whether both pumps were delivering fuel. But that was without pressure build up so I get your point..
I do recall hearing different sound from the 2nd pump. Can hear a more distinct "fuel swirling noise" inside the tank when pump 2 is energized.
Wish I had the pressure gauge in possession, as I had to return it.
I need to check fuel press not becoming really low onder WOT to eliminate this cause entirely.

Cath-converters, I checked through the exit of them.
--> LH cat honeycomb looks clean and is not moving when pushed.
--> RH cat only has the upper part still installed. It is not loose, but looks dirty and has some melted part here and there .(looked with flex cam)
Downstream sensor is in center of the cat, behind the remaining honeycomb when looking from direction of gas-stream. So it should get converted gasses. Maybe the non lineair gas stream caused by missing downstream honeycomb after the sensor is causing alarming CO value? (I can't read downstream sensors value on ELM327/phone.
I will check whether RH is clogged somehow. I have exhaust cutout valves per side I can compare flow per side perhaps.

Strange thing is that there are no codes indeed.
-High charge air temp does also not throw codes.
-Knock sensor oversensitivity also no codes in some cases I believe (over/under torquing of the sensor?)
-(partially) blocked cat does not throw codes I now understand.

I have some history of the car, but it is such that it could be anything. (Horror story, driven till engine seized without any maintenance in 2016, then overhauled engine installed by a someone, and that driven until seats dropped in 2019...I suspect at least the replacement engine never ran well and has cluttered for 4 year at PO, until I bought a "nice project":-))
As it is a project, it is luckily not my daily.

Thanks for the help all!

 

Hmm, could this be an XK8 engine (higher compression), hence knock at high boost (and your pulley on top)? Maybe see if you can locate UNLEADED high octane race gas and get better results. Not sure if a basic compression check could tell the difference between an XK8 and XKR engine.

 

When I purchased the car the valve seat were dropped so I had to to replace one cilinderhead. When the engine was opened up I could see the pistons top surfaces those being the ones from XKR pistons in lieu of the XK8 pistons, but yes I have checked again later because this seemed a mistake that suits te profile of previous ownership.

However, today I remembered something else that i deemed irrelevant earlier...
Front tires are standard size, 255-35-20, rear should be 285-30-20,....BUT IS: 285-35-20. Trac on or off makes no difference in car behaviour, and I never see a traction loss warning light in the dash too.
Would this deviation in tire size be the hidden culprit? I just tried to drive carefully with low tire pressure (1.6Bar) but that pressure difference did not result in a solution so pumped them back up..
If this is it then I might hit myself for ignoring it earlier;-).