First off, after many many months of looking I've finally bought myself a used (2009) XFR! Very happy with it so far, however I've come across a couple of little niggles and would like some opinions on possible causes, because I can't recreate the problem consistently so don't think it'll be an easy diagnosis...

When on a long drive a couple of days ago, cruising steadily at around 50mph (1500 RPM in 6th), I went to accelerate gradually and the car began to slowly judder forwards and backwards - revs build up a little, then drop back repeatedly as if it was struggling to accelerate in the gear it was in. Kicking down and then immediately back up it would be fine (the car can accelerate gradually in 6th no probs), but when I put it back into D (hold the upshift) the problem repeated itself. Backing off the accelerator stopped it, as did pushing harder so the car changed down. Putting the car into S mode also 'cured' it.

The same thing happened once the day before when pootling at about 30mph - I downshifted manually and it stopped so I thought it was a one-off - but on this longer drive (when the engine was properly warmed up) it began to do it consistently for about 15 minutes. Since then, I've done a couple of long(ish) drives but it hasn't repeated itself yet.

Having had a google on the subject, the symptoms seem similar to a faulty MAF sensor or leak somewhere, except that it only occurred when in D and at quite a specific engine speed (1500 RPM). Could a dodgy battery lead to my symptoms? The thing that makes me think it could be a battery is that the tyre pressure warning lights have been on and off sequentially since I've had it (different wheels each time), along with the 'washer fluid low' warning - all are fine.

Thoughts or stories of similar experiences welcomed!

 

Where are you feeling it? Engine ? Transmission? Rear end?

I had a failing mass on my old jag that showed up when cold. If I started it and tried to hold a steady idle around 1200-1500 it would stumble.

 

First thing I would do is look to see if any codes have been stored to see if the onboard diagnostics can help point you in the right direction...

 

For me two possibilities come immediately to mind - dirty MAF sensor(s) and/or auto transmission fluid overdue for a change.
I'd start with the quick simple easy thing first, clean your MAF sensors. Takes 5 minutes tops, just get a can of MAF sensor spray cleaner, remove the sensors, spray them clean and replace.
If that doesn't fix the problem then I'd look at a transmission fluid replacement, not easy or cheap, and in any event your car being 7+ years old it probably needs doing anyway.

 

Thanks for the suggestions. The judder motion is felt in the whole car (it feels like its lurching forwards then backwards around once per second) - even my wife noticed it when it first happened.

MAF sensor was one thing that cam up on my google search. I hadn't thought about transmission fluid, but that was going to be on my list of things to change on the next service - if it is the cause, it'd be nice to get that done under warranty! I'll have a poke around the sat-nav tomorrow to try to access the onboard diagnostics (I think I read somewhere how to do it).

 

Are you still under warranty then? If so, would definitely have the dealer work it out

 

Your 2009 is very close to the old S Type with the 4.2L engine and 6 speed ZF transmission.

Any chance it could be the torque converter locking and unlocking?
Drive the car and keep it out of overdrive. It's hard to do because the late model transmissions will lock up in other gears beside top gear.


Do the symptoms match anything in this TSB?
Just a thought?
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The dealer wasn't able to re-create the judder problem, so they 'reset the gearbox' and the problem hasn't re-occurred since so fingers crossed that's sorted! Might be related to that technical bulletin for the S-Type.

I'm now looking for excuses to drive places!

 

If he has an XFR that is a 2009 he might not be in the US, likely Europe. They didn't sell a XFR in 2009 in the US, but it sounds like they did in other countries. The XFR has the 5L supercharged so it would not be related to the S-Type R 4.2L Supercharged.

 

What's the mileage on the drive plate? (simply put, mileage on automatic clutch pressure plate)?

 

When you get a used car, make sure you change all the fluids and get suspension sorted out (bushing, mounts, etc.) Your car is very heavy and the mounts will show its wear over time.

 

I'd be looking at changing the tranny fluid too.

Having said that the transmission controller does have a memory does it not? After driving for a while it memorises your driving style. If the car is new to you and you are using it differently to the previous owner (like puttering along at 50mph constant throttle) perhaps it just hasn't learned your style yet?