Greetings Jaguar Community,

I have recently purchased a 2007 Jaguar XJR X305 with 70k miles with impeccable service history. I picked it up in DC and drove it back to Central Texas as way to bond with the car and learn about its 'quirks and features' to quote Doug DeMuro. I have fallen in love with it, but also discovered a few 'eccentricities' that I would like this community's help understanding and identifying the right course of action. I'm new to Jaguars so apologies in advance for my ignorance.

On my 1.7k mile journey I encountered the following issues:

- Fuel level dropped to empty when the tank was half full. It would remain at 0 for a few minutes and would pop back up. This repeated 3-4 times over a 40-50 minute period and then never happened again. (not a major issue)
- Adaptive Cruise Control worked well (for an early system) for the vast majority of the trip. However, after about 2-3 hours of driving occasionally the system would disengage and ask the driver to intervene. At that point I couldn't re-engage cruise control, with the warning 'Cruise Control Not Available" popping up when attempting to re-engage. After turning the car off to fill up gas or even for only a moment the system would return to normal and work for hours sometime without issue.

Additionally about half way through the trip the check engine light came on with the following codes:

- P0171 - Lean Bank 1 Condition
- P0174 - Lean Bank 2 Condition
- P0101 - MAF Sensor Circuit Range / Performance

Clearing the codes did not resolve the issue. But I removed the battery to get it tested and that has extinguished the light for now (battery is in good order). In regular driving or even generally spirited driving there is no indication of any performance issue, but when you floor it from a standstill the power is immediate and strong until a clear power drop off between 3-4k rpm before it comes surging back. When the car is driven very aggressively - there is a sense that there isn't full power all the time (sluggishness and hesitation). When the car returns to normal driving at any speed power delivery is clean and smooth.

Cold start idle is rough but quickly normalizes.

While some of these individual issues have been addressed on this forum before, I was wondering if the confluence of these issues makes it clearer where the potential cause may be coming from.

Most recent service records from previous owner outline the following:
- 07/21: "P0171, 174 codes check visible components for vac. leaks and security, nothing found. Trim reads ok. Cleared codes. Road test no repeat of light."
- 04/21" "P0171, 0174 codes. Found and repaired 1 vacuum leak."

In the coming weeks to plan to clean the MAF sensor (once the cleaner comes in - lots of shortage of it apparently) but beyond that is there another good place to start given the confluence of symptoms outlined?

 

P0171 and P0174 are respectively right-hand cylinders combustion too lean and left-hand cylinders combustion too lean. Possible causes are:

Air intake leak between mass air flow (MAF) sensor and cylinder head
Fuel filter/system restriction
Fuel injector restriction
Fuel rail pressure (FRP) sensor fault (low fuel pressure)
Low fuel pump output
HO2S/catalyst monitor sensor harness wiring condition fault
EFT sensor fault (low fuel temperature)
Mass air flow (MAF) sensor fault (low intake air flow)
Exhaust leak (before catalyst)
ECM receiving incorrect signal from one or more of the following sensors; ECT, MAF, IAT, fuel rail temperature

I would usually think air leak as the most likely cause but your observation that cold start idle is rough suggests either the ECT (Engine Coolant temperature) or IAT (Intake Air Temperature) sensors may be faulty.

Graham

 

With the gas gauge. In my 2004 X350 when my sunroof leaked it puddled water under the backseat and it shorted out the wires. It gave me all kinds of flaky errors until i figured out what it was. It's just a thought.

 

Fuel gauge problem are not unknown.

The float clips on to the side of the plastic bucket containing the fuel pump.

Root cause likely to be bad connections on contacts due to corrosion.

Replacement float and potentiometer are not expensive

IAT bulb is adjacent to the MAF wire so can be cleaned at the same time.

Adaptive cruise can be problematic-I don't have it and don't want it! lol

Good luck

 

If the previous suggestions, have been exhausted, & found not to be the answer.
As was my 04's situation
There are eight rubber type gaskets, inside the intake manifold.
Not a horrible job, the instruction's, with pictures, were a big help, as always.
Took a while, getting used to everything on a disk though.
Instead of the traditional, paper book, shop manual.
Advantages are;
No longer required, to be very careful, not to smudge the pages, just print another.

 

If you plan on driving it hard on a regular basis, once sorted out try these. You did not mention suspension. Coil overs or air struts?
1. Service transmission
2. Check motor mounts
3. Replace transmission mount.
4. Serice brakes and differential.
5. Clean injectors
6. Change plugs
7. Replace front O2 sensors.
You will end up replacing them anyway. A 15 year old year is due a refresh.