Hi All,

I have 2007 XKR, I found at high speeds (post 100 KPH) and at post 4000K revs the car started juddering from full to the floor acceleration, if felt like is was going over cobblestones (whole car juddering) at high speed. if i came off the gas it stopped completely be it 100 KPH or 150 KPH - no gas smooth as silk, as it was related to heavy heavy pushing and only started at high speeds and not the 0-100 range full power.

would there be anything specific related to this engine judder only at high revs and high speed?


Many Thanks!!

1st post and 1st jag :-)

 

If the engine is running smooth then I would check the drive shaft , transmission mount and motor mounts.

 

Also worth checking that a bolt or any other part isn't missing from any of the driveshaft components - an out-of-balance driveshaft can cause a hell of a vibration.

 

Wondering if you are describing the same thing I noticed on my 2010 XKR under full throttle, high revs, acceleration in 2nd gear, going steep uphill. Mine is a rather violent jerking, as if the engine controls were cutting ignition in and out. I still have not looked into it more but, think that it is actually the engine computer cutting power due to something like low octane gasoline and resulting detonation.

 

I've experienced similar 'surging' on full-throttle acceleration in my 2010. I believe it is as you say - the engine is detecting the onset of knocking and is backing off the throttle to prevent it. Which is why I always run it on 98 RON (US 94 octane) rather than 95 (US 91) when I'm planning some hard running.

But the OP is talking about shuddering rather than surging, which I take to mean a vibration rather than the on-off-on effect of anti-knock.

 

i just bought an 07 XKR and it has the same issue exactly,, has this been to any conclusion?

 

I have fixed the issue.....

the catalytic converters were on their way out and suddenly they went under a bit of gumph..... engine limited performance came on and the next day i limped to the garage, new plugs, leads and catalytic converters and a completely different car, sadly not as noisy.... i thought it was the genuine exhaust noise... but hey ho.... zoom zoom now.....

the reason for the jumping was that the engine could not get the air out so it so jumping with the pressure at high speed./pressure.....

i was hammering it before to work out the issue and all makes sense....

if you lived in Dubai like me this was a 2000 GBP issue to fix, with a 38% discount!! (they felt sorry for me as ive only had the car a month) however saw the parts online much less.... its was timing and availability Vs cost and discomfort etc.... im happy, love the car.... move on!

best of luck!!

 

Ouch!!

 

I have been searching high and low for someone talking about the annoying vibration. I know this is a very old post, but do you happen to have the TSB number for this? Thanks so much in advance!

 

Annoying vibrations aren’t normal.
You don’t have a signature block describing your vehicle so it is hard to be anything but generic…
Nor do you describe the vibration, when, where, under what circumstance…
Bearings, bushings, worn driveshaft coupler, worn differential, worn supercharger snout, worn idler pulley, tires, bent rims, worn cv joints, … the list goes on.

 

I was replying directly to the post which is relevant to my issue: "a very common drone that occurs at the 1250-1350rpm range and is such a common problem on 07 and 08 XK's that there's a TSB on it. It emanates from a resonance in the exhaust/ catalytic converter."

2008 XK 4.2 N/A

 

JTB00088
You can find a link to it in post #6 in this thread:
XK Vibration

There are quite a few posts on it in various threads, including one where a user posted a drawing of one of the brackets.