2005 XK8 60,000 miles in good order but - - - - -
Dash Engine light has been on for several months and simple DIY computer reports DTC P0171 System Too Lean Bank 1
Proper Jaguar garage computer apparently reports both banks running lean.
More recently accelerating quickly or going uphill results in Restricted Performance dash light with obvious restrictions.
The engine light now stays on permanently but the Restricted Performance light clears by itself if I slow down and doesn't require the car to be restated to clear it.
Generally at Restricted Performance light doesn't come on if driving at <50 mph although it will cruise on the flat at 70 mph without Restricted Performance just as long as I take my time to accelerate up to 70 mph slowly.
Otherwise the engine is running sweetly and the car goes fine without any misfires etc.
So basically the problems occur when the engine is powering under load.
Lambda sensors seem OK.
Petrol filter replaced but doesn't help.
Several engine air leaks sealed but still no joy and symptoms persist.
Jaguar Garage mystified.
Any ideas please would be much appreciated.
Thanks

 

Exactly which air leaks have been sealed?

 

Jaguar Garage wasn't specific but said there were several hoses that they fixed and that the engine was now seal tight.
I'll phone them on Monday but I think the answer could be a bit vague.
IMO they probably want the car back to make further checks for which they will inevitably and understandably charge.
Such is life !

 

Assuming the garage checked your system properly, there should be no EVAP leaks. Does your car have an EGR valve?
My guess would be a leak on the EGR system because the EGR valve opens under heavy load or acceleration.
On my XKR supercharged 4.0 engine, there is a metal pipe from the RH manifold to the EGR valve and that pipe can crack, causing air leaks.
Air can get sucked into the inlet if the valve is open. Stuck open EGR would also allow too much flow in but it would be at all times.
If you don't have an EGR valve then it does not apply. Just thought I would ask.

 

Thanks for the suggestion Alan.
To be honest I have no idea whether the 4.2L (not supercharged) engine has an EGR valve or similar.
Can anyone please advise
Thanks again

 

I checked online and the Jaguar parts dealers show that 2005 XK8 does indeed have an EGR valve similar to my 2002 XKR.
The EGR valve is located beneath the throttle body and is difficult to see from above.
Attached service bulletin is for the XJR but it shows the layout which is similar to my car, and the transfer pipe which could be leaking.
Again it is just my guess that a leak would allow fresh air to enter when EGR valve is open and cause lean running under load.
That would explain the symptoms you described. I don't think the EGR is faulty.
You could see the transfer pipe if you remove the air intake runner (from the air box to the throttle body)
However there is likely a shroud over the pipe and it is still difficult to inspect. Maybe use a small inspection mirror.
You probably need to take it to your mechanic to check it and to do the repair or replacement.

 

Thanks Alan
Most helpful

 

@Splash: WOW!....have the exact same issue....P0171, sometimes P0174.
You can read through my postings of what I have done in trying to solve this with so far no luck.
I currently have all fuel injectors removed, in process of cleaning them, checking spray, replacing O rings and such. Thought is that perhaps air is leaking pass the bottom injector O rings.
I was about to take into local Jag dealer, see what they could find, but after reading of your results.....glad that I did not and saved the money, time, etc.

IF you are able to solve this, PLEASE post the solution and I will do the same.

Later,
LannyL81

 

Check the plastic air intake ducting very carefully. Including the air box lid and seal. Common to crack with age and use.
Helps to post all the codes the car is throwing? The garage should have written what trouble codes were found on your paperwork?
If not I would ask them too.
.
.
.

 

Another thing to check is the MAF. I don't see that listed as one of the items serviced. A faulty MAF can cause lean codes on both banks.

 

Regrettably I seem to be making little or no progress so far with my 2005 Coupe XK8 no with 61,000 miles.
Of course the original problems with the CEL remaining permanently on, plus the temporary Restricted Performance message when the engine under load, which eventually self clears if I back off the power.
But as of yesterday, as well as the above, I now have a DSC System Fault message and the ABS light on !
This may clear if we get a few sunny days.
Needless to say that the Speed Limiter and the Cruise Control are now unavailable.
However the car drives just fine if I drive like an old lady going to church and only gradually accelerate to 70 mph.
So I've decided to take a look at the codes for myself, although I don't really know much about modern power units.
My intimate knowledge of Jaguars relate to my old Mk II Mk X models.
Consequently I could do with some sound advice please.
Starting from scratch, since I don't yet have any suitable diagnostic equipment, which is the most suitable OBD port interface and App to purchase (Preferably from Amazon) for the XK8 please ?
I have an Apple iPhone & iPad plus a permanently installed in the car Samsung Tab 9 Android, which is primarily used for the Google Maps APP and for playing my music through a Bluetooth cassette in the original sound system.
(Not the greatest quality but good enough for me)
Any advice from discriminating users would be much appreciated.
Thanks loads.

 

If you search here you can find a few threads discussing code readers for Jaguar, including this one:
https://www.jaguarforums.com/forum/x...ol-xkr-165423/
Personally I use Autophix 3210 which is available on Amazon for about $30.
It has a lot of different screens to help with diagnostics, and my favorite is Datastream that shows all the sensor data from the ECM computer.
For example, IAT and mass flow rate will tell you if the readings from the MAF sensor look correct.
Same with the oxygen sensors, fuel trims etc. All good stuff.
Regards,
Alan.

 

Thanks Alan
Your prompt response and valuable comments are much appreciated
It's good to chat with a happy user and I think I'll get one of these
But before I do, just reading through my thread to pick up on the relevant points:
1) Is the Autophix 3210 compatible with my 2005 XK8 ?
2) Will it report on the things like Restricted Performance, Banks running lean, possible EGR pipe leak, faulty MAF etc ?
3) Will it report on DSC System Fault and ABS light also Speed Limiter Unavailable ?
4) Are you using the Autophix 3210 Red or the Autophix 3210 Pro and is there any advantage in using the 3210 Pro ?
5) Can the device be left permanently plugged into the interface or will it discharge the car battery ?
Thanks loads

 

Attached is a list of codes for 2003 XK model. Probably works for your car, but there might be an updated list for 2005 models. Try looking on the following Sticky:
https://www.jaguarforums.com/forum/x...ts-data-29800/
Any scanner will read P-codes which are Powertrain codes related to engine management and emissions.
Most scanners do not read B-codes (Body) or C-codes (Chassis) and DSC would fall under chassis, unless the fault is engine related.
So the Autophix is compatible with your XK and will read P-codes. There are fault codes for any sensors related to emissions but you cannot always rely on it
By that, I mean that the car's ECM can set a code for a sensor fault if it recognizes it, but often does not know what is causing the problem. It tells you symptoms.
You can read data from MAF, MAP and other sensors related to emissions, as well as fuel trims to help with diagnosis.
I originally purchased my blue Autophix for my 2006 BMW 750i car and it has enhanced functions for BMW, so it shows all the systems including SRS, brakes etc.
As far as I know, Autophix does not have enhanced diagnostics for Jaguar so you need a different scanner if you want to see body or chassis codes.
You can leave the scanner plugged in without causing problems. It has a very low current drain so it would take months to run down the battery.

 

Thanks Alan
I'll buy one the and report back with any useful findings

 

Splash - by the way I am from the UK (born in Northern Ireland).
My brother still lives there and has owned many Jaguars over the years.
He currently has a 1998 XK8 and a 2012 XJ (diesel). His son has a 2008 XF 4.2 Supercharged.
Also his son is a motor mechanic so I have technical help by phone when I need it!
Regards,
Alan.

 

Oh dear
I've been unsuccessful fixing the EWL and Restricted Performance Warnings when under load with running lean codes.
And also I'm now getting intermittent DSC System fault warnings too, which are sometimes accompaied by the speed limiter disabled.
(The cruise control hasn't worked for 5 years !)
Today out of the blue the drivers window lost its closing setting and parked 1" open, so I had to reset it, which makes me wonder if there's a battery issue.
My exceptionally expert Jag Dealer/Garage seems baffled, so I've bought an Autophix to run all the time I'm driving to see if it records anyting useful.
I already have a Samsung Tab 9 mounted over the old Satnav display, which is currently running Google Maps, and I've now loaded the Autophix software.
However I'm having trouble actually locating the OBD2 port on my RHD 2005 XK8 Coupe.
It doesn't seem to be where I expected it to be, so I've not yet been able to plug in the dongle.
Does anyone have a guide/photo please ?
And if anybody can throw some light on my issues that would also be much appreciated
Thanks

 

Good News Everyone
After months and months of suffering with restricted performance, false/bogus dash messages and nonsense reports from professionals, amateurs and indeed works diagnostic computers, I am relieved to announce that the situation has been resolved, no thanks to any garages or "experts".
Needless to say that I'm reluctant to calculate how much this scenario has cost me over the past year.
Well, I'm somewhat embarrassed to share this information, but here goes.
I'd pretty much given up trying to resolve the situation and accepted that I had to keep my revs under 1800 and drive like a granny going to church, when just by chance I noticed that the driver's side window wasn't fully closing.
Now, I'd encountered this in the past when I hadn't driven the car for a while and my battery wasn't fully charged, however recent diagnostics had only recently reported the battery was OK and adequately charged.
Anyway I rectified the situation by the usual lowering of the window until it clonked procedure and then raising it again and waiting for the clonk.
That appeared to solve the window problem until a couple of days later the issue re-occurred.
So I popped down to the auto-shop and bought a new battery.
Replacing the battery turned out to be more challenging than expected, as I inadvertently dropped a retaining nut down the side of the battery compartment, however eventually a magnet on the end of a bit string saved the day.
Battery now installed, I reset the window again and drove off to visit relatives.
To my amazement all the dash error messages disappeared and, when I floored it to 5000 rpm, there were no restricted performance errors.
Everything worked exactly as it should.
I've now driven circa another 2000 miles without any errors or issues, so it seems that all the grief I've been suffering over the past year has been entirely due to a dicky battery, which none of the garages, experts or diagnostic computers detected !
Driving my XK8 has again become a pleasure
One final point
When I took off at speed, my drivers side window was open and the wind got under the headliner which has now dropped

 

So the bad news is that the replacement battery didn't solve the problem for more than a couple of days and the running lean messages and engine light returned with a vengeance. Anyway thank you all those who provided me with their much appreciated advice. So now in desperation after driving like a Granny since 2024 I recently tackled AI on the subject, which gave me a list of probable causes at the top of which was the fairly obvious MAF sensor replacement. Now my Jaguar specialist garage had been chasing this problem for 2.5 years without success with solving the issue, despite a plethora of significant invoices. So following the AI advice I investigated the MAF only to discover that the installed module was the original build part from 2005 with a seriously blackened leading surface of the sensor component. A much appreciated immediate response and delivery of a replacement Denzo module (without blackened sensor component) from Berkshire Jaguar Components solved the problem immediately and now hopefully my Granny driving style days are now over. But now I have a dilemma. Obviously this is something that the Jaguar specialist garage should have, and I thought had, already checked but clearly not. Should I continue to use this garage and should I tell the owner who seems to be an awfully nice chap and how is he likely to receive the news ?

 

Why burden the shop that didn’t fix the problem with the news that they are incompetent ??? Will that really solve anything to have that conversation ??? Why not just take a sharp stick and poke the shop owner in the eye ? That will do you, and him, just as much good.

just move on to the next issue and hope that a new garage will be more useful.

Z