Being a new member, I might get away with this blasphemy.

My question is this:
Does your XKR really feel like a (~n almost) 400HP car?

Iīm asking this because mine isnīt.
Please note, I havenīt been to a dyno or done any injector cleaning yet and so I donīt know how many precious horses have run away in the course of 16 years.
I also acknowledge that this might be a very subjective feeling.

During my search for an XKR I have driven XK8īs and XKRīs - none of them felt more powerful than my current one (also not really feeling the power difference between an 8 and a R), however, my main car is a Range Rover Sport 3.0 HSE that has almost 300HP, but I think throttle response and initial acceleration might be better than in the XKR.
Maybe it all comes down to the car being so quiet, but the Range Rover isnīt a sound-beast either. So I donīt really know.
All I know is, that my XE-S had about the same amount of power and it was a rocket. Touch the throttle and you were off, being pressed into the back of your seats.
I kind of expected something similar.

Stopping my rant and thinking aloud now and would really love to hear about your experiences, insights and yes, even feelings.

Thanks in advance.
Berglmir

 

The boring answer is that you now own an older car, possibly with a partial/unknown history. It is now up to you to bring the car back to its original level of performance. Start with aggressive maintenance, gather some data, take a hard look at all the subsystems.

Check the throttle cable adjustment to make sure the throttle opens all the way when the pedal reaches the floor. The sensor is by the brake booster/master cylinder bin. Some of the slack can be taken off for better response. This is a zero-$ fix, too.

Check the fuel pumps (the earlier car has 2, and they both come on under power). Check the fuel pressure. Replace the filter.

Check the intake, air filter, air flow meter, fuel trims, etc. Track down and fix all air leaks.

Check the boost level. Get a gauge and check the pressure at various rpms and load levels.

Check the extra water pump for the inter-cooler water jackets. If it is not functional, intake air is likely too hot, so less fuel and less power.

Check the supercharger seals for leaks. There is a redesigned part.

Look into a supercharger rebuild. My superficial understanding is that the rotor/case clearance becomes larger over time and leads to secondary flows and loss of pressure or air too warm. Of course there is always these after market pulleys folks talk about.

Best of luck, keep us posted.

 

Also realize there 2 fuel pumps, are both working? I purchased a 2001 XKR for my wife several years ago and have basically rebuilt all the mechanicals in it over time. Just completed valley hoses and supercharger rebuild also.

The reason I ask is when we first got the Jag it did not seem to have that performance that I expected until we had a fuel pump failure. It was after I took out the tank to replace them, I figured we were had been only running on the one pump that was beginning to fail. Once I replaced both pumps the performance was dramatic.

Hope that was helpful.

Mike

 

Great input! Thanks a lot.

The 2 Fuel Pumps issue is very high on my "to be checked" list and I will make sure to go meticulously through the list fmertz has suggested.

The "older car" argument is valid, however I used to have a 1971 Triumph TR6 and although it just had measly 130HP the way this car applied itīs power to the street seemd more "dramatic" than the smoothness of the XKR.


But weīll get there. Eventually and with your great help!

 

There is something wrong if your XKR isn't quicker than your Range Rover. Make sure the gearbox is in Sports mode and it should feel very much like a 0-60 in 5.2s car.

 

My 2005 XK8 has had multiple owners and had sat untouched/unstarted for about a year, so there was quite a bit of maintenance to be done. There was an embarrassing lifter "ticking" noise at startup for several minutes and performance was unimpressive/boring, but hey, the car looks great....

My 2012 Hyundai Genesis, with a 3.8L 333hp V6 coupled with a ZF8 trans, was much, much more responsive, requiring me to use a lighter foot on the throttle (and brakes) after driving the Jag.

I replaced a quart of oil with the same amount of Marvel Mystery Oil for 500 miles (then a full oil change), which removed the start-up ticking. Then, 8 oz of MMO in each of 3 full tanks of gas honest-to-goodness felt like it doubled the perceived horsepower. (I think the throttle body was gummed up, resulting in the disappointing performance.) Everyone has their opinion of MMO, but I am a big advocate. It has saved me a lot of time and money over the past (many) years by trying it prior to component teardown & rebuild. Just my $.02...

 

Sports Mode definitely helps, I know.
The Kick Down works too, but with some lag.
Itīs like this:
Flooring - Klick - 1 second nothing - BOOOoooom (meaning lift off, not the engine exploding )

I donīt like the 1 second wait.

 

Great input Redline.
I think that this is what it comes down to:
The car was used by the previous owner to drive to work...5 miles each day.
Took care of the car, did all the inspections, but essentially never DROVE the car.
So I will exchange some fluids, clean the injectors, check that both fuel pumps are working properly and go from there.
I might be tempted to check the actual power on a dyno - so at least I know how subjective my "lack of performance" actually is.

But one step after the other.

 

One thing the XKs are geared pretty high for cruising, the Range Rover lower for off road use. Off the line the Range Rover may very well feel quicker as a result. Once moving and in power band the XKs go nicely but they are a bit of a pig off the line.

 

Exactly what I experience. Thanks Enderle.
Just another excuse to browse the Forum endlessly for some mods and improvements

 

Granted my STR is a bit newer but there's no 1 second delay and the challenge is not to spin the rear wheels off the line.

OBD live data and dyno should show you if all's OK but it sounds iffy.

 

I would start at throttle cable adjustment and MAF sensor cleaning.
My car was never sluggish but these two items made a notable difference to response.

 

Berglmir,
Don't make the mistake of driving an X150, 5.0L XKR, the amount of power difference and the drivability difference to the 4.0L XKR will shock you. I have both and there is simply no comparison. Having said that, I still love my 2002 XKR for the sense of class and the special feeling you get when driving it. I am completing a complete restoration of my 175,000 mile 'vert and should have the car back by the weekend. AND I CAN'T WAIT! It's so beautiful, and you feel so special with acres of walnut veneer surrounding you, who cares about the reduced power and the loosey goosey handling. I also get my newly restored 1972 De Tomaso Pantera back this weekend after 4 years. The new 500+hp, 550ft.lbs. of torque engine in a sub 3000lb. car should be positively frightening. Honestly, I look more forward to my X100 returning to the stable. (Much more comfortable to drive).

 

I think my 2007 XK feels more powerful than my 2003 XKR did. Throttle response was better and car seemed peppier. The XKR did eventually kick in, but I was surprised at how sluggish it was off the line compared to my other cars-- but thats a skewed comparison to high power, newer, cars.

You may be down some HP, the Mina Intake Tube helped throttle response (maybe placebo) but I was happy.

Best!
dsd

 

You might want to try this other technique: when you want more power, press the gas pedal down some (not all the way), but QUICKLY. If you ease gently on the pedal instead, the computer interprets it as meaning you want more power and opens the throttle some, but stays in the same gear. If you press the pedal and it goes down quickly, the computer thinks you need power NOW, and starts with a downshift. This works very well with my ZF 6HP26, this downshift takes a fraction of a second. This quick downshift is great for passing, etc., or just a quick fix of V8 noises in a tunnel. On the other hand, pressing the pedal slowly builds power slowly, then eventually downshifts. By that time, the pedal is much further down and it downshift a couple of gears, revs too high, not always what you had in mind, and feel too late. Again, you have the Mercedes trans, but one would think this has to work the same way.

 

before you do anything do a proper compression test on all cylinders and use a mechanical gauge to test oil pressure over the RPM range. these two tests tell you the most about a lot of your engine block hardware.

 

Change the MAF .

 

The transmission on these cars has the habit of learning your driving style. If you haven't had the car long enough, it may still be adapted to the previous owner's putting around. Do a battery reset and you will notice the transmission will behave differently. It will adapt to your driving style.

However, if you want something more dramatic and money is no object, an LSD with lower gearing will certainly help with acceleration and drifting if you like going sideways.

 

I had a similar very slight hesitation in pick up at one stage.
Buy a can of MAF cleaner, clean the MAF and adjust any slack from the throttle cable. Cost a few dollars and 30 minutes of your time. You will notice the difference.

 

He is right. Cleaning the MAF is very easy. However replacing it is better. Its one of the few changes on the car where I noticed a difference in performance.
If you look at the start of this forum you will see there is an non-jaguar part that is exactly the same for a fraction of the cost. https://www.jaguarforums.com/forum/x...2/#post1277384 (save you looking it up)

Will see if I can find you a 'how to' link.

Here you go. Cleaning https://www.jaguarforum.com/showthre...l=1#post780676