03 XK8 6 speed. When I take off then punch it she falls on her face then goes.
I know the 5 speed has this problem but I thought it was fixed with the 6 speed.

 

Have you already done the accelerator cable adjustment procedure?

 

I have two Jags just the same Lox. They are both 4.0L V8's - a 2002 XJ SE, and a 2000 XK8. There is a lag in the throttle response. I also have another yr 2000 4.0L V8 Sovereign, which as soon as I touch the accelerator, is gone!! Infuriating!

 

As Jon89 suggested, adjust the cable, easy to do.

My 03 has no hesitation.

On the left side of the firewall under the hood there is a large flat black cover, take it off. Inside you I'll find a small black box with the accelator cable going into it. Unclip the cable and adjust it out a couple clicks, don't over do it.

If you have a scanner you can read the % throttle opening when you press the gas pedal.

 

One thing the 6spd won't do is downshift into first gear so if you take off, let it shift and then punch it, you will be pulling from a low rpm in 2nd.

 

The accelerator cable IS NOT connected to the throttle plate. It's connected to the PPS (pedal position sensor). That feeds volts to the ECU, which in turn feeds info to a stepper motor connected to the throttle plate. The TPS (throttle position sensor) then works out the actual throttle plate position and tells the ECU. Adjusting the cable just removes the play in the pedal and nothing else.

 

I had thought this also but my 03 seems to start out in first.

In sport mode, gear selector in 2, take off from a dead start and accerlation is crisp, transmission up shifts into second. It difinetly up shifts without changing the gear selector from 2. So, I can only guess it's starting in first. With Manuel selection I get an up shift all the way through the gears.

Now done shifting it does not apear to drop below second.

Beats me....

 

The ZF box will start off in first so long as you have come to a complete stop (or very near so). But once it shifts into second, there is no going back until you stop again.

That's why I say, if you start off slow and it shifts into 2nd before you floor it, it may well be pulling from less than 2000rpm.

Sport mode helps (some) since it will hold the gears a little longer.

 

with or without traction control on?

 

That's very true but there are those here who have played around with adjusting out that extra slack so that the throttle body opens quicker/more fully. So even though there is not the direct connection to the throttle body itself, doing this adjustment is almost the same as if it was directly connected.

Doug

 

+1. If you connect an OBDII scanner and monitor throttle %, you can see that with a slack cable that you may not reach 100% throttle when flooring it.

Also, if you drive gingerly most of the time, try driving aggressively for awhile...the computer is programmed to adapt to your style.

 

I think I've argued this out before. If you are driving along at 50mph and want to accelerate, there is no slack in the cable because you've already taken the slack out by putting your foot on it to reach 50mph. It is true that a slack cable might stop you getting 100% open, but who drives like that?

The best way to describe the problem is my Sovereign (which goes instantly) has the accelerator pressing on a lever opening the throttle. The SE and the XK however have a sponge between the lever and the throttle.

 

Hey Jim--I know what you are getting at. My XKR also does not seem as responsive when tapping the pedal as other cars I have owned. In particular, my wife's 2012 Acura TL jumps when you barely touch the pedal and I am pretty sure that car also uses a drive-by-wire setup. The reaction on the Jaguar does seem pretty "damped" in comparison.

Doug

 

Yes Seismic - I only really noticed how bad it is when I got the Sovereign. Touch the throttle (even at 70mph) and the nose instantly lifts. The other two Jags just don't do that.

 

I'm wondering if it might have something to do with the throttle body connection plugs (high resistance?). They are really naff. I might cut them off and solder in a new (bigger) plug. Anyone know offhand how many wires there are in the two plugs?

 

My 2004 xjr has throttle response is leaps and bounds beyond my 2001 xkr. My xkr has complete tuneup...Cable adjusted...No codes. It leaps to life when the happy button on the throttle gets nailed..But besides that..EHHH. Never driven another one so I cant compare it to anything but my xjr

 

The PPS / ECU / Throttle motor is an electromechanical servo and in common with all other closed-loop servo systems does have some dampening. If the system were undamped then the feedback starts to compensate for it's own control voltages at an ever decreasing level (hysteresis) - this will eventually cause the loop to oscillate and be uncontrollable.
The damping is implemented as an electronic lowpass filter, either fabricated from analogue components or (more likely) within the ECU's software.
This lowpass filter also has the advantage of evening out fluctuations due to light wear and dirt on the PPS.

 

Yes but the damping in this car seems quite extreme. It appears to me that this was intentionally programmed in, just like the slurring through the gears of the automatic transmission.

Doug

 

Hi, just to add to the comments, I bought a 2012 2.2 Diesel XF 3 months ago and have the same problem. When coasting up to a roundabout and need to go, there is a 1-2 second delay whilst the car decides which gear to use. By the time other cars are crawling over my boot I have pressed down further on the accelerator to evade collision, the car has dropped a gear or two and shoots off whilst loosing the rear end in wet conditions.
My service team team say their jags do the same. Surely this can't be true. Does anyone have an answer?
I have owned an X Type and S Type both petrol before this XF.
I am so disappointed I want to give it back and buy a completely different make of car.

 

I can't speak for diesels - they have limited rev bands and are different to petrol engined cars. However, what I can say is that not all Jags are equal. I have 2 that are sluggish, and one that goes like a rocket! Trouble is I just can't find out why.