Hi Everyone.

so I have had my throttle bored. It is from a 1999 XKR (the one with the vacuum chamber on the top of the throttle body for cruise control). It is now at 82mm. I disassembled and reassembled the throttle body, gave ti to an engineers and have fitted it back.

I originally got very high idle with it hunting high and low and on a blip of the throttle it would go high but stay high for a while. I have hard reset the electrics and it is running better. At around 950 idle and smoother but I am getting a p0507 code.

I have a few questions.. What is the adaptation procedure as I want to see if I ave done anything wrong and whether the car can find its own correct idle... Engine runs smooth, I cannot find any air leaks. have checked and pretty sure all is ok on that side.

Another question, there are two adjusters on this throttle body, one on the throttle cable side (grub screw with locknut) which adjusts the position of the throttle position sensor in relation to the cable and one on the other side of the throttle body (again, grub screw with locknut) which adjusts the position of the butterfly stop.

From anyone having had their early body bored.. what did you find was the best way to get the idle down.

I have jaguar diagnostics and a mongoose cable. Is there any advice that can be given?

Thanks in advance

 

The only software adjustment I know of consists of slowly pressing and releasing the gas pedal to the floor and back, several times, ignition on, engine off. This is supposed to be done after the typical gas pedal cable adjustment. Hard to be positive it does anything for double sure, but the cost is right and it is hard to see how it could mess things up.

Separately, I believe the throttle plate angle is available over the data cable (possibly even over OBDII). It is worth checking the evolution of that number as the as the gas pedal is pressed. Maybe yours does not start near zero. Most complain it does not reach 100% at WOT, hence the cable adjustment procedure. You can also pull the intake elbow and check the throttle plate visually as well with a helper pressing the gas pedal (ignition on, engine off). Maybe the "zero" degrees position as read by the ECM is still leaving the throttle plate at an angle, hence the high idle.

Last bit I remember, there is a video out there of a frustrated XK(8/R?) owner fixing a high idle after a throttle body repair/replacement and finding no easy answer. 99% chance it is on YouTube. From memory, it involves an adjustment at the throttle body itself.

Best of luck, keep us posted.

 

ok, thanks...

a bit more to add... when you trn the ignition on, you hear the throttle body clicking and going to the motors 'closed position' which i can also visually see down the throttle if i look.. no other codes are thrown...

also, something i had never seen before... as i was checking this.. i pushed the throttle right down.. and the butterfly moves to about 80% under my control of the pedel-cable then slows down as if the motor (or mechanical guard perhaps) takes over and puts it to 100%.

will try the repeatedd pedal to the floor on position 2 as you say.. yes the ocst is right.

it has been interesting dismantling everything and seeing how it all works.. i am calling this my covid project... not much else to do.. stay in and stay safe...

 

This seems promising: high-rpm-84948

 

yes, thanks, some interesting pointers there.. the adjustment of the throttle position sensor is for the later type with the tps on the outside..

i may do some adjustments... theres scope but i dont know how it will affect.. will be interesting to see...

 

Maybe this might help.... or not

 

I know this is a very old thread and not sure if anyone will even respond but I must try lol..... I have noticed the other day while cleaning my throttle body (2013 xfr 5.0 supercharged) that the throttle plate doesn't quite close all the way and there is maybe a 4 or 5mm space and when pushed with a finger it moves and sits flush all around. Is there a way to adjust it so it closes completely or is it suppose to have that little space?

 

no1 (nice name although a bit presumptuous)

This is the X100 forum for XK8 & XKRs, so probably you won't get much of a response on your later 2013 XFR.
However from general knowledge, to see if you have an issue, I would first gauge how high rev your car is when it is idling. As you're probably aware your car should start, from cold, rev-ing high and then settle down. But if it stays high rev-ing, I would guess you have an issue. Not driving the car, if the initial high rev settles down after a minute of so, I wouldn't be concerned. Most modern cars auto correct the air fuel mixture according to the trims but that takes time for things to get up to operating temps.

Again from general knowledge, the throttle plate shouldn't be completely closed at idle as this would cut air off and engine will die. If the throttle plate doesn't close completely when the ignition is off..... who cares!

 

The ECU will control the right opening for the rpm needed. The reason why without ECU control its more open is for failsafe mode, so when the throttle control is disabaled due to a failure, by having the throttle go into a larger default opening, the ECA can still control the engine via fuel injection.

 

Thank you both David and avos
I know I was posting on an XK thread
1. It was the first one I came across
2. U seemed knowledgeable in an area I had a question about
3. It wasn't a model specific inquiry and more of a general question on a specific part that supercharges have across the board
I do thank you for sharing your advice with me and easing my mind in this matter.