Can you be more specific about what a "Putt Putt" is?

 

How hard you hittin' the burritos?
It could be normal since the ECU richens the mixture just a tad when you let off the gas to produce a little burble in the exhaust.

 

Needs more description for sure. Is this like a hard shift point or power stuttering? Just motion and not a sound? Level or inclined roads?

 

Mine does a little surge about there when cold. Kind of a rich / lean / rich / lean 3/4 of a second cycle. Nothing obvious but it's doing it. I assume it the replacement o2's aren't at the same spec as the factory stuff and take a couple seconds longer to hit reliable temp. Or my exhaust is more open. Who knows.

 

 

 

What you're describing could be the same as my Range Rover 5.0 S/C, which is obviously the same engine.
It started doing a weird thing where I would be driving along, and if I had the throttle on light , just keeping steady speed at maybe 40-50 mph, it would gently judder until I either lifted of or pressed on the pedal. When it would then be perfect again. I did manage to trigger an error code related to MAF on 1 drive.
It concerned me enough to get the car serviced and the gearbox checked as it just felt like the drivetrain was juddering, I thought the gearbox was on it's way out.
What cleared it for me was to take the two MAF sensors out (easy on the RR) and give them both a clean out with brake cleaner spray. Never did it again after that. I think at least one of the sensors was dirty and just operating outside of it's normal parameters and triggering ECU conditions which then caused the juddering on partial steady throttle.

I've not had the Jag do the same thing but if it ever does I'll be giving the MAFs a good blast of brake cleaner before anything else.

 

 

I would think plugs would present in a more dramatic fashion as well as more consistantly at idle. Though I may be mistaken on that as this is SC and I've had little exposure with them. As indicated above, it likely has something to do with air/fuel mixture and MAF would be a good place to look as well as fairly easy to clean without doing parts swaps. If you haven't checked yet, look for any codes that may have been thrown.

 

 

Great car. It's the third one I've had and this time I decided to go for the S/C version. I had the TDV8 version before and although the diesel was impressive there was a little momentary hesitation as the turbos spooled up which started to grate after a couple of years. So that was all the excuse I needed to go and get the 5.0 S/C engine.

I've had it two years now, I've done about 15k miles in that time, it's now at 103K miles and all I've had to spend on it is two services and a water pump.

Stonking car, could even be quicker off the line than the XKR as it can put the 500 bhp through all four wheels; and like the XKR it gathers speed very quickly all the way up to whatever speed you dare to go to .

 

If you have the 550 PS version, the RR does 0-60 in 4.7; the 510PS version is 5.1. The 4.2 XKR does 4.8 (coupe) or 5.0 (vert), while the 510PS 5.0 does 4.6 and the 550PS does 4.0.

So, depends on which RR you compare to which XKR, but, like for like, the XKR is quicker. Despite the 4WD traction, the RR is significantly heavier - minimum 4762 lb vs. 3693 lb)

 

When I say 'off the line' I meant just that.. off the line for about 100 yards. I'm well aware the Jag will leave it for dust after that, I've got them both in 5.0 S/C (510bhp) guise.
But try and get off the line too quick in the Jag and it just spins up!

 

DO NOT use brake cleaner of any kind on the MAF sensors or it will destroy the coating on them. Use only cleaner designed for cleaning MAFs.