Thanks for the help. A new development is that I now have P0171, P0174 and P1582. I  do have the Jaguar option on my Autoenguity so can do the tests you suggest, although I am a novice with cars generally, what is a WOT?? So far I have changed all the ingition coils and used a petrol suppliment to clean injectors. That did help a bit but the fault codes have returned and the car has generally not run wellthroughout the period of the problems. I also had a fault code on the traction control switch and a light bulbs either side of the clock have stopped working so I have eletrical faults also!!

I will try to email some screen shots from the autoenginuty I have some red boxes on the EVAP system flow checks. It also shows the freeframe data with fuel trim numbers when the faults occur.  Other than that the only other symptom is that it engine feels generally rough.

I have not looked at the spark plugs yet.

Many thanks

Jon

I have replaced all the coils but hadn't looked at the spark plugs as the dealer replaced them c 3 months ago. I took them out last night - see photo attached. They are shown in position of the cylinders viewed from insdie the car.

What do you reckon??? 

Two on the right side look very oily and burnt and one just burnt. 

Is the amount of oil a concern, i.e. piston rings need replaced or could failing coils have done the damage??

Does the gap look right?

Is there any way of telling if indeed the dealer did replace them c 3 months ago?

I note that they appear to have a code stamped on the metal ring, 7 match, 1 is different - the one that looks in the poorest condition (top right)??

Any comments would be appreciated.

Thanks & regards

Jon

I replaced all the plugs today. Car seems to run fine but the fault codes persist. The pattern is still a period of restricted performance that lasts c10 mins then goes away, or if you stop and put the car into Park generally the restriced perfomance clears.  Also the hesitation under acceleration remains.......   

The car is booked into a specialist on Monday, will see what happens!

thanks

Jon

Jon,
1 bar is one atmosphere which is 14.7psi therefore 5 bar is 73.5psi. That could be the problem if you are only getting 55psi. Have no idea how you change the pressure though. Cheers, Roy

Terry  Can you offer any way of checking the fuel filter? Indeed can you tell me where it is !!  I can see the tank from the boot but can't see the filter????

Thanks Jon

Getting more difficult indeed.

Have they done something regarding possible fuel injector restriction?

If all that is done and found right, I think it would be interesting to know if whilst having the engine under some load  and still closed loop (as it doesn't appear when running in idle) to check the lambda values with a external meter. If these values are the same as what it should be, you can take the conclusion that the O2 sensors and the ECU are at least working/reacting right. And then I would still keep my bets on fuel delivery.

If it is off, then of course there is either an air leak before the O2 sensor (or o2 sensors not fitted right?)  or the ECU isn't getting the right info/isn't working right. But it will depend a little on the outcome of the Lambda test.

The above could be done for instance on a Dyno.

Just a thought,

After this more unlikey things could cause this all. For instance, it is far fetched, there could also be an ECU issue. I have heard of some going bad, but these where the older pre 2000 4.0 cars.

Maybe reprogramming of the ECU might be a thought, is cheap, and who knows what has been done to the car/ECU before. At least you ensure you have a clean program where at least Jaguar is sure of is right.

Next, incomplete burning or issues with engine timing for instance.

Thats it for now with ideas,
Andre.

Thread resurection! I am having a similar issue with my xk8. If I was say driving along at around 10 mph, then hit the throttle hard (possibly not full throttle) then the car seems to stutter before continuing on as normal. Sometimes it will stutter 3 times as it moves through the rev range. If it stutters badly enough it puts the car into its failsafe mode. Shutting off and restarting doesnt clear it, but I have found that if I shut off, remove the lid from the coolant header tank under the bonnet and then restart it is fine, seems like there is a build up of pressure, but could be coincidence. Car also reports low coolant level, although the coolant level is not low - i think this is just a dodgy sensor but i guess it could be related. I am looking at doing a coolant change, thermostat and fuel filter. If the lambda sensor isnt too expensive i may do that as well, although the car just went through its MOT and the emissions looked fine - and i would think that they would show up a lambda issue.

Anyway, i would like to see (if your still around) if your issue is definately gone?

I have read that partially blocked fuel filters are the root cause of many a difficult to trace problem. It is not uncommon for garages to have ignored replacing them at the specified intervals even when car has FSH.
Perhaps ypu could post the bill for all this work?
Cheers