Hi, got some new issues with my Jag. Some history to understand the whole picture.
It all started with some smoke coming out of dash into interior. Stoped and towed the car to the repair shop afffraid, that something may be burning.
Repair shop have found that some kind of plastic head cover in the engine bay had crack in it. and while giving load to engine, it let the smoke out, that got to interior. Seemed like it was changed and fixed. but few days driving had diesel smell in the car.
Only few days passed, and one evening at the moment i started driving home, got Charge failure message. Got straight back to repair shop. The alternator was dead.
They found that it is not charging at all. The diode line was burned. Also saw that diesel is leaking from the gas return pipe on the top of the engine near fuel injectors.
The return pipe was changed. The alternator was repaired. Got the car back and drove out into traffic jam and noticed nothing wrong. But, there is but.
Just when the road was clear, tryed to drive faster, and reaching 3k rev, the gear wasn't changing. If i keep the pedal at the same level, engine starts droping revs to zero. If fuel injection was not enougth, car started shaking a little.
I am able to change geras manually. But i feel some punch at the moment of change. If i drive in very light mode, not exceeding 2k rev and pushing it slightly, the gearbox works fine and changes fluently. Everything seems to work.
But if i just try to overtake someone giving some push, the torques dissapears.
Back to the repair shop. The car shows no errors. They found that one of solenoids does not give any information to ecu. Changed it, but the problem is still here.
I have no idea where to look for the problem.
I thought maybe changing fuel return pipe (that goes back to fuel tank), they damaged something with fuel injection and fuel flow. As the torgue disappears only when i need more fuel on bigger revs.
Next i thought, maybe that is the problem with fuel filter. It does not let bigger flow. Maybe it got clogged. after fiel pipe change. But why i get no error of any king? Even connecting the pc, it shows nothing.
(it reminded me of problem with my Volvo, when i got fuel filter cloogged - found out about it when pushed the pedal and endine just stalled. But after turning it on and driving at very low revs, i could somehow get to repair shop. Even stalling 8-10 more times after reving up too much). But pc at least game me engine error. At this time i got nothing.
I am thinking if that may be something with gearbox. But then it would not work fluently on low revs and in manual.
Maybe actuator burn got more problems in some othe places? I am afraid that it could damage ecu, or gearbox, or fuel pump. Also wouldn't want to change every element of fuelling system.
The repair shop do not think, thaat it would be fuel filter.

Any ideas? What to try, where to look. Because i'm trying to understand, why most Jags are kept so well and have so low milage - they really just stay in repair shops.

 

By your description i suspect that your 2nd turbo don´t come in the play when rews rises in the area when it should join the game. (between 2.5-3k) Because there was an alternator work i suspect that the vacuum line what operates the valve for the twin turbo boosts has been disconnected from the valve actuator during the alternator work. The valve are sitting in the boost valve body on front low if the engine, just visible when looked down between fan and engine.

 

Thats a very good point. Because they tryed to drive the car with diagnostics pc on board, and it did not show any lack of pressure, gas flow or anyrhing else. Dissconnecting of turbo would not be indicated and i understand that i would ahould feel lack of power at 2.5-3k revs. But why i am loosing tourge even holding the pedal at same level? If turbo does not work, it should work as atmospheric engine. Except the moment that engine gets too much fuel as second turbo does not provide enough air. And the engine is choked by too rich mixture.

 

Fuel trim are linked with measured airflow, so choking would not happen. However: On turboed engine the boost comes from exhaust pressure = fuel. When you lose energy of exhaust side you also lose boost, so you are correct to suspect the injection side too. When everything are measured and calculated these don´t work as atmospheric, like fully mechanical injection models. If you lose vital measurements there are an safe ("limp home") chart in engine managment module, for basic running with limited power output ( around 100hp ) and you have engine warning light on dash.
As the power loss issue started when works done to the engine, i would re-check every connection / every joint around the areas worked. The plastic head cover what had crack on it, was an air intake manifold combined cylinder head valve cover. It is possible that something went wrong allready on that work. The change of that cover requires removing the fuel high pressure piping and injectors on that side of engine. (there are two intake manifolds for each side of the engine.
On top of the engine are air intake tubes with O-ring seals. It is possible that these are not positioned correctly and high pressure strech one out. Specially the main intake tube to the engine, what have circklip holding two pieces together. (top front of the engine) Also it might be that the fuel hoses are in wrong order in fuel filter.
On alternator side of the engine, right above alternator, are also an small well hidden sensor for 2nd turbo boost pressure sensor. Since the alternator are in very tight spot it might be that the pipe of that sensor have been accidently got hit? However: You should get engine warning on dash and limp home mode if the measurements related to the rpm/load are not correct. (Exept if you car have reprogrammed ECU for exsample bypass the EGR:s? Some low quality ECU programmers might just wipe out all errors)
You might want to download the service & repair manual from the Sticky section of this forum. From manual you are able to locate all sensors/solenoids/pipes.
You mention that PC was conected to the engine: Do you know what diagnostic software been used? Januar SDD? On Jaruar SDD diagnostic software there is an test routine what are used to diagnose engine in different boost/power areas. When runned it will ask operator to keep engine in different rpm levels for a time to do checks of operations of solenoids/pressures etc. After process it will give possible causes for issues. (it indicated correct faulty/sticking solenoid for my issue some time ago -> pressure release solenoid. After cleaning it worked fine, but i changed it anyway)

Btw: The common low mileage are not because of Jags are fragile. It is more about owners. For your information the V6 3.0 litre diesel engine used on Jags are in fact made by PSA/Ford and mounted in much larger volumes exsample in Peugeots and Citroens. https://en.wikipedia.org/wiki/Ford_AJD-V6/PSA_DT17
I have 2010 model XJ 3.0D, now just under 300k km (187k mil) on clock and all original parts under hood, exept serviced filters/belts/rollers and one solenoid. Used only recommended oils since new and changed 10k km (6250 mil) intervals.

 

I was trolling a little bit with Jags time in service and totally agree with you that it much refers to the owner. With your knowladge of mechanics and Jags, no wonder that yours is in top shape.

I will tell all your ideas to repair shop tommorow first thing in the morning. After manifold cover change, the torgues was fine for few days, except diesel smell coming inside from time to time. The torgue issue appeared only after alternator repair. So hope that is only a turbo sensor.
The car had DPF removed before i got it. So the ECU was reprogrammed. The repair shop after rebuilding the engine told me, that they saw some reprogramming, so they reseted the ECU, and cleared the DPF error on their own. That did not cost me anything additional. So seeing in this forum, how much DPF removal and reprogramming costs, i wonder maybe they actually did some cheap reprogramming for error ignoring. Thats why the turbo error is not shown.

 

Ok, then i believe that something have been accidently disconnected during alternator job. It is tight space.
Never seen it, but spotted from pictures that 2nd turbo boost sensor are mounted between alternator and engine, with one screw to the upper alumium mount holding serpentine belt tensioner/alternator.
Much easyer check are the vacuum operated valve controlling boots between 1st and 2nd turbos: On next to airfilter boxes are vacuum valves. Follow pipes what goes down front of the engine to find correct one and try suck it. You should see the actuator moving the lever on valve. (down front of the engine) Next to vacuum valve are electric solenoid for boost release. Check connector & wires.
The main ECU programming are time consuming process, so i believe that your shop just erased the fault codes, what are fast operation and therefore they did not charge you. It seems like all engine fails are wiped and therefore you don´t have MIL-light on dash for any error or Limp home mode.

I am on my first Jag, but been born with wrench in my hand. Newer worked as car mechanic though. (even went thru the mechanic school in young age)

 

They checked the turbo and actuator connections below. Everything seems connected. The gas return pipe was changed, but it only lets gas back to tank. Everyrhing near it us also in tact.
they say ecu gives them error for turbo- lack of turbo pressure. But they looked if turbos open and close normally. Cleaned all pipes around egr.
Thinking that it could be maf sensor. Because after disconnecting it, the engine does not drop revs or chokes.
but it also may not be the cause.
is there a way to check if it works without finding working one and replacing it?

 

There are 2 identical MAF:s in 3.0L diesel, one for each turbo intakes. Top one are for 2nd turbo and low one for low rews. You can swap them and see if the problem moves from high rew:s to low rews.
Did they remove the alternator to check 2nd turbo boost sensor? If it have been teken the hit, then error from missing turbo pressure are for sure.

 

Thanks Vasara for you ideas. After few weeks of trials and errors, and consulting with Jaguar dealership service found the problem.
It was fuel pressure regulator. After changing it everything went back to normal. but still trying to understand the connection between error of turbo pressure lack and the torgue falling above 2500 rpm.
Maybe regulator gave too much fuel and ecu saw that turbo pressure is not enougth for that ammount. Or regulator just did not provide enougth fuel pressure, but then the error would be different.
At least it works untill next time it fails somewhere.

 

Ohh.. Thats a mystery. However its good that your XJ works now and hopefully this helps somebody else ending on same issue.