XJR SC Poor performance when requested

[Lordgaz]

Hi All-
I have an issue with the perfomance of my 2004 XJR SC - Its been running fine for almost a year of ownership, and the previous owner advised they had serviced it with new plugs/oil before selling to me - but recently, when I put my foot down, the car is a little reluctant to perform - Tootling around it is fine, but under wide open throttle, it is hesistant / fluctuates as if not receiving enough fuel. Taking accelleration gradually, I can reach all desired speeds
My local garage read off the code 1582, but this is not a direction to a specific fault it seems

I did check the emissions recently, and one tail pipe gave quite a lot higher readings than the other pipe (that mechanic supposed it might be due to a hole in the muffler, but not sure about that)
What would you do? - Any similar experiences here?

Cheers
G

[J44EAG]

I would begin by cleaning the MAF and MAP sensors. They get covered in black, sticky crank case breathr residue. Use spray switch or carb cleaner.

The MAp sensor is on the tube immediately after the air filter box lid and is held in place by two small Torx screws. Just then pull out the sensor. Note the hot-wire in the assembly. DO NOT TOUCH with a hard implement when cleaning. Spray cleaning only.

The MAP is at the back of the engine. Remove all inlet trunking, then get down the back of the throttle body to the supercharger elbow. again Torx screws hold the sensor into the charger elbow. Best to remove the throttle body, get a new gasket before starting the job. The throttle always gets hugely caked in gunk. This all needs removing.

If you are a DIY guy with a reasonable skill set, these jobs are possible.Otherwise, sub the work out to a Jaguar specialised garage.

Mike

[Lordgaz]

Hi Mike

Many thanks for the reply.
The MAP sensor replaced middle of last year - it was a pig of a job for the mechanic - I am not getting any codes for this sensor currently or the MAF sensor (which I had already cleaned, but no effect on the problem) -

[J44EAG]

Do you have any codes at all showing or indeed any dash message centre pointers?

Mike

[Lordgaz]

Hi mike
The only code is P1582..no dash messages or lights

[ptjs1]

Lordgaz,

In a situation like this, I'd replace the fuel filter unless you absolutely know it's been changed in the last year.

As regards the P1582 code, that could be a bit of red herring. See here:

viewtopic.php?t=9295

Good luck

Paul

[Lordgaz]

Lordgaz,

In a situation like this, I'd replace the fuel filter unless you absolutely know it's been changed in the last year.

As regards the P1582 code, that could be a bit of red herring. See here:

viewtopic.php?t=9295

Good luck

Paul

Many thanks for the reply Paul - I certainly cannot say for sure that the fuel filter has been replaced - So going to go down that road initially (My local Jag specialist also suggested it could be throttle position sensor on the throttle body or the pedal (eg - the electrical tracks get worn and give out spurious information) - I have checked the output of the throttle pedal and it seems to change voltage smoothly - but I am not yet tempted to buy a new/2nd hand TPS for the throttle body - It feels like fuel, but that could be due to mechanical blockage or technical (engine management) issue - I note in the video you linked to is was for XK8 - do you know if there are one or 2 filters on the XJR and their locations? (I will have a google of course)

[J44EAG]

On the XJR 2003>, it is above the dirt shield immediately behind the N/S front wheel.

The panel screws and clips will be well corroded so expect a fight. Releasing fluid will help but not much... Have some new clips and screws to hand before you start the job. Some screws are into captive nuts within the chassis rail and the nuts spin in their captivation when you attempt to turn them. They are very poor quality. Changing the filter is easy. Getting those abominable machine screws removed is not! Get the car up reasonably high on some suitable ramps to make access easier. I`ve got away only removing half the screw set and packing the under-shield down enough to get at the filter before now.

I forgot about the filter in my diagnosis. Paul is correct. Those filters can and do fill with water from the fuel. Sometimes what comes out of a fuel filter defies belief. You wonder how the car could have kept going with so much crud and effluent in the system.

Mike

[Lordgaz]

Ok, car has been stripped down a little - There are a number of air leaks around the throttle body, and I need some help with some points.

There is a pipe which "push fits" into the plate which the throttle body bolts onto (throttle body base?) - The pipe should normally be released by pushing in a collet which releases the pipe - but the collet seems to be missing and the pipe was held in there by luck - The pipe is also damaged (could be repaired, but also looking to see if replacement is available)

The question is, can the throttle body base be serviced to replace / repair this collet (I do not have any images or schematics for this part of the car, if anyone can help)

Pipe part number appears to be 4W93-9D289-BB

Can anyone (Mike?) assist

[J44EAG]

I managed to break that pipe when removing it. I agree the fitting can be unco-operative.

XJK in Stoke on Trent are particularly good at brainstorming what parts you need. They have more incentive being a private supplier than a Main Dealer parts man in my opinion. Given that parts diagrams are rather poor at the best of times, identification is the biggest issue. Then there is the fact that there are several different numbers for the same component. ie the American 4W93 part has to be converted to a more typical and recognizable British Dealership part numbers listing beginning with C2P, XR8 etc. Note also that the 4.2R is fitted with the American sourced Eaton 112 cfm supercharger with various part adaptations to make it talk to the Jaguar 4.2 engine. It all gets a bit obscure and convoluted when it comes to sourcing the correct parts first time.

If you are ripping this engine down for overhaul, I would suggest you also obtain a length of 1/8" (3mm) ID vac/pressure pipe from the Jag network or from Halfords. Those little pipes fall to bits and can cause fault codes and restricted performance codes when they fail. Now is the time to replace whilst you can get at them. £8 should fix that issue at a main dealers or about a fiver for in my opinion, better quality pipe at Halfords. See some of my XJR super-charger threads on the X350 engine section. Guidance with images will help you through this difficult maintenance area.

Valley hose failure with old age and mileage is common. This is the hose that runs under the charger (charger needs to come off) and is usually living on borrowed time after about 80k miles and about ten years on the road. XJK will be able to source that for you. Also obtain a new throttle body gasket, remove the the throttle body and clean of all crank case breather residue. It will be filthy! Use carb claner. The same goes for the MAF sensor at the rear of the throttle body to charger elbow. This sensor sits in a trench which again fills with congealed breather residue. That needs clearing. Also attend to the MAF sensor downstream of the air filter. The hotwire gets covered in gunk. Spray carb cleaner to get the crud off.

Removal and cleaning of the EGR valve is desirable. It is a b`strd of a job to get off. The two small 8mm hex bolts are hugely difficult to shift due to obstructions. Ask any Co-coordinator with an XJR what he thinks of this overhaul aspect and almost without exception they would describe working this overhaul as totally evil! I ended up putting my job out to the trade due to those difficulties and my vicious sciatica which stopped me finishing the job myself.

Mike

[Lordgaz]

Thanks Mike. As you can see in above photos, the lower throttle body elbow is caked in black. It is the same for the actual throttle body (and the back side of the butterfly. ) I need to clean it, but I’m a little paranoid about damaging the coating mentioned so often (is it PTFE?) .. You mention cleaning with scotchbrite pad etc in your posts, so where abouts do I need to be careful?

[J44EAG]

The coating extends about an inch above and below the throttle plate. It is reasonably tough but you should only use a soft rag and loads of carb cleaner on that coating. You will also find the throttle plate circumference to have a hard coating of crank case breather oil baked onto it. All the contaminate must be removed. Pay special attention around the plate spindle ends where they pass into the throttle body. A soft tooth brush will help in that location. Properly cleaned, the throttle plate should snap shut under spring influence.

Throttle cleaning is a filthy job so use nitrile gloves. Gunk on your skin is difficult to get off and is highly toxic.

I only used Mild Scochbright to buff up the areas other than on the PTFE coating. The coating is easily seen so just stay off it with the Scotchbright and you won`t do any damage.

Cleaning the charger inlet elbow is not so easy without the part on the bench. Unless it is removed which is not easy, you will just have to make as good a job of it as you can. Some of us have also taken the opportunity to remove the dead ridge of metal that the maker failed to machine out under the throttle body and gasket. This causes turbulence to incoming charge air and reduces performance. Similarly, removing blunt edges and restrictions in inlet trunking, gas flowing the elbow and doing the same within the charger, all help towards de-restricting what is a fairly choked up and constrained engine. This is the Jaguar 4.2R`s biggest bogy. Strangulation of air flow both on the inlet and exhaust sides of the engine. See my "Tuning the V8 for power" where I discuss the issue in much greater depth.

Mike

[Lordgaz]

Excellent reply. Thank you Mike

[Lordgaz]

Hi Mike - I have the throttle body and elbow on the bench currently -
I have used carb cleaner and a paint brush to clean up as best I could on the throttle body (and I can see clearly the area of coating)
However, there seems to be a slight ridge of deposits where the butterfly comes to rest - Should I leave this alone? or do you have any tips for removal - Wary of damaging this coating.
The elbow is very black and dirty - carb cleaner and brush is not shifting this easily

[Lordgaz]