I don't think it has anything to do with cable adjustment, I have checked my throttle position with AutoEnginuity and it opens to 100% but I do have this sluggishness. I posted on this before with my reasoning below.


I pretty much never use the J-gate and just keep the card in D, but I do find it to be a bit of a pain as the various ECUs conspire to get the transmission into as high a gear as possible with the end result that the rmp ends up at around 1500rpm where there is very little torque.

Now if you want a bit of power, anything more than a tickle on the throttle causes it to immediately drop a gear or two before doing anything, so just when you need a bit of power, what you get is a delay then a lurch into a lower gear.

So I think the issue is being caused by Jag trying to get as high as possible MPG figures at the cost of drivability.

 

In the old carburetor days I remember changing out the little plastic accelerator pump cams--different profiles would alter the amount and timing of the squirt of fuel into the carb so that with the proper cam the car will really jump. The modern equivalent to that was some electronic gizmo that you could plug into the throttle body sensor to alter the air/fuel mixture or something by fooling the ecu.

Doug

 

They are called a sprint booster, been around a few years. The change the transfer function of the throttle pedal potentiometer.

 

That was done last summer.

 

I think this what may be what I'm feeling. I may be punching it as its shifting into second and I'm expecting it to go back into 1st.

 

With it on. I think I've only turned it off once.

 

On my car I can eliminate the gearbox ECU because 'tickling' the throttle doesn't prompt a gearchange - I wish it did! It just squeezes the sponge a bit more.

The XK is in having the underfloor rust proofed. I've asked the Tech to check/clean the two connectors to the throttle body, but I've got a good mind to cut them off and solder the wires.

Incidentally, when I first raised this issue someone said it could be the MAF. So I took the MAF out of the 'good' Sovereign and put it in the crap XK. No difference!

 

When traction control its going to fall flat on its face when its about to spin..At least feels that way to me

 

This is exactly what I do. I live by a very high speed intersection and do not want even the slightest lag when I punch the accelerator. If i just suddenly punch it I get a definite lag every time, If I ease in and then punch it there is no lag at all. Hopefully this continues to work because I hate it when a car delays under heavy acceleration.

 

OK, two issues here. Firstly, yes, even in Sport Mode the car shifts to a higher gear fairly quickly unless you are really pushing it a bit, so when it is in that higher gear and you then give it a lot of gas, there is a lag time for it to shift to a lower gear before it really reacts. Secondly, though I very seldom drive my car aggressively and give it full throttle I have noticed that it responds better to a more steady and controlled pressing of the accelerator, rather than an instant push all the way to the floor. If I think that I am going to be in a situation where I will need to speed up quickly, such as when I am on the merge lane on the interstate behind a car that is going pretty slowly I will manually put it into a lower gear and keep the revs up at around 3500-4000 and then if I nail it, it responds immediately, rather than the delay that it would normally take to downshift. In that scenario there is no lack of instant response.

 

For months I've been disappointed in the response of my car. Sometimes it seemed passable; other times it was inexcusably lagging. Downshifts were unpredictable and sometimes ragged.

I focused my attention on the transmission though, because I hadn't trusted the two shops that last serviced her (including a Jag dealership). I finally sucked it up and serviced the transmission myself to the proper level with Mercon SP. I don't know what the transmission has to do with the engine, but EVERYTHING is better now. She launches quickly, pulls strongly and downshifts CONSISTENTLY (what a pleasure that is).

Try properly servicing your 6-speed first and then see how you feel about the engine. The procedure is a PITA, but at least with the MERCON SP you won't break the bank.