Hopefully you experienced XJ owners can help:
A dear friend bought a used 2013 supercharged XJ several months ago with approx. 35, 000 miles. Recently, on multiple occasions she has experienced very rough and/or severely delayed acceleration when pulling from a stop, or merging with traffic. She has an extended warranty, so she took it to the Jag dealer that sold her the car.
After more than one month at the dealership, they have called her to tell her they can not find any problem with the car, and upon test-driving it, they can not duplicate the problem.
She doesn't know what to do at this point: They have admitted that they have not fixed anything since they could find nothing wrong with her car.
Suggestions??
On a separate issue, she experienced the dreaded dead battery twice, and has since had the battery replaced. Do these cars require a battery tender like the XK's if not driven for every day or so for long distances?
She is ready to bail and take a substantial financial hit.
Thanks

 

The poor acceleration could be caused by a very low battery not having enough juice to power the computers properly.

Have her keep the car on a tender while not in use and see if the stumbling problem goes away.

 

Lots of people here heartily recommend using a battery tender but I've routinely let my car sit for up to ten days without a problem. I guess everybody's experience is different.

Dwayne

 

I don't think it is a battery issue because the car is running and the alternator will be providing more than enough electrical power. It is peculiar that no fault codes have been thrown up as the ECU software is set up to detect anomalies of running. It could be poor petrol but who knows ? If a Jaguar dealer, (presumably this is an official main agent) can't find a fault, then then next time it occurs the circumstances need to be carefully noted down.

Did the dealership deal with the flat battery problem ? It is known that cars left unlocked can remain "awake" with a number of electrical items drawing current. How long is the car left between journeys ? My MG TF had a totally flat battery after winter, and was left unlocked in my mother's garage. As far as I know, no lights were left on, but me not locking the car may mean they stay on.

 

My 2013 has sat as long as 5 weeks and stared up just fine. There were major changes throughout the XJ for 2013 and that resulted in much better battery behavior among many other things..

 

Yet similar problems have been documented on other Jags, I saw it myself on my S-type. It costs almost nothing to at least try charging the battery.

 

Thanks for all the replies and suggestions.
I have advised my friend to get a battery minder to keep the battery up to full between driving trips. Appears she has not gone more than a day or two between use.
If all else fails, she has an attorney lined up to help with the uncooperative dealer she purchased the car through. At this point, if she experiences any further unreasonable/unforeseen repeat issues, she is prepared to turn the car back in for a loss-but for peace of mind!
Too bad these beautiful cars aren't more realistically reliable........

 

But they are. Her car has some simple problem, just needs a little patience and effort to track it down.

 

The dealer has had it for over one month, and can find no problem to fix.
Unacceptable.

 

Apparently they could not reproduce the problem. If they were taking the car out for frequent test drives, that might be a clue right there.

 

Seems like a rather hasty complaint about a specific dealer who is apparently trying to help. Nothing at all to do with the general reliability of the cars, which is known to be excellent. Don't let that stop lawyers spending money...

 

Tossing in a recommendation. I would grab the car from the dealership and take it for a drive. See if I can make the problem occur again. If the problem is still there and is tending to hang around, get back to the dealership and ask them to sit in the passenger seat as you drive the car. Let them experience the issue since it may be something as a driver that is causing this.

I have seen in the past where a dirty idle air control valve will cause the engine to idle rough/erratic. But, that did not normally result in poor acceleration. I guess the other thing that I would say to try is to start the engine and then get your hands on the wiring for the throttlebody. Move the wiring around and see if the motor acts up. It is possible that there is a corroded/dirty pin that is causing the throttlebody not to act properly and depending on how the car is driven, it may cause it to be more noticeable under certain conditions.

 

Out of interest where is the idle control sensor located ?

Mine is a diesel I have cleaned both MAFs but still getting a shiver at idle .

Sorry for thread hijack.

 

Mine is a '12 which I bought almost 3 yrs. ago. After buying mine I became aware that these automobiles need to be locked. I even lock mine if I go into the store for just a few minutes and when it's parked in the garage it's always locked regardless of how long it is in the garage. Have NEVER had a battery problem and this automobile is 5 yrs. old.

 

Thanks for all the feedback.
She finally got the car back from the dealer about a month ago with a new battery and has it on a battery minder since. Car kept locked when not in use.
Today she gets in the car, starts it, puts it in drive and nothing. Car will not move. She presses the accelerator and the engine revs, but no movement, nothing. She releases the accelerator.
She puts the car in park, with the engine running. Then places the car in drive, presses the accelerator again and the car starts moving. She is experiencing the exact same thing she experienced before. It's as if the car is not in drive, but in neutral. When the accelerator is depressed, the engine revs, but the car does not move.
Sounds like a transmission problem, if it weren't for the fact that this happened previously when merging into traffic and getting no response when depressing the accelerator.
Anyone want to fathom a guess? The dealer that she purchased this car from, and who subsequently cannot find anything wrong with this car, is an authorized Jaguar/Land Rover dealer in Washington state.
Thanks for any input.....

 

tnt10, the first thing I would check is what the fluid level is in the tranny. Unfortunately, this is easier said than done as you have to get under the car and pull a plug on the side of the tranny to check the fluid level. Having a lot fluid level can cause the tranny fluid pump to not develop sufficient pressure to engage things, leading to a neutral condition. Otherwise, you may possibly be looking at a bad pump too.

 

Does this trans have the shifter cable fastened to its side (2 x 8mm bolts) - they're known to come loose/drop out if so.

 

Seems to me to be a pressure or valve body issue. First question is is the proper fluid in the transmission? Second I would try another drive selector module. Third I'd make sure that the electrical connections between the selector knob assembly and the transmission are all clean and properly seated. Did the dealer give a detailed description of all the things they tried and checked? In my nearly 5 years with my SuperSport this has happened to me 2 times where the transmission hung in first and it turned out to be that i had accidentally flicked the up shiftier paddle. Just my wild guessing here.

 

As XJsss said there have been reports of the shifter (selector knob assembly) causing things like that. Solution was to replace the entire assembly.

If it's under warranty maybe suggest that as a problem?

Not very common so I am guessing.
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