Ok, more like a bucking bronco!
Thought I had noticed this just before packing my '07 XK away for the winter, so I had to check when I pulled her out today to start some projects.
With the transmission in P, I slowly press the gas peddle down as I watch the tach.
When it gets to 4500rpm, it suddenly drops to 4250 (based on the tach hash marks), rapidly climbs back to 4500, drops to 4250 again. This continues to repeat if I hold the gas peddle steady, or press down harder.
Backing off the gas returns to steady rpms, if I stay below 4500.
Any thoughts on what could cause this? Some sort of limiter?
Just got the car shortly before packing it away, so I'm not familiar with Jag quirks, but it seems odd, never seen this in a car before.
Thanks for any insight.

 

You don't have any codes on the dash? Sounds like a high speed miss but not under load. When you drive the car and take it up to 4500 in 1st or 2nd gear does the car buck. How many miles and did you ever change the plugs. Can't see it being a coil pack as if it was you would throw an MIL code.

 

I know that on my 2002 XKR you can only rev to 3000rpm in park or neutral as a limiter steps in to take control. My guess is that it may be the case with your car as well as a protection.

 

Jaguar XKs have a built in rev limiter programed to kick in at about 4000 rpm in neutral. That is what you are experiencing.

 

Thanks guys, that's kind of what I suspected (rev limiter, since I've got no codes). I'll try it on the highway, just be sure.

 

Like others have said, there is a rev limiter in park or neutral for the XKR. I think it is as 4500 rpm or so. I think the owners manual says.

 

Ok, took her on the street, 6000rpm, smooth sailing. Got to be the limiter, learned a new thing today (never had that in a car before).

Thanks again!

 

From the owner's manual: