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There is a cable to the 'throttle position sensor'. It's electronic from there.

 

I would really like to know the 'adjustment' procedure, my pedal=>throttle is a little sluggish, I thought that was just normal.

 

I remember reading something about this on the "other" forum. Here it is for whatever - I haven't tried it:

: SHOFZR on 2010-04-23 at 22:01:02(posted from: Host: 99-67-115-135.lightspeed.rcsntx.sbcglobal.net IP: 99.67.115.135) Subject: 100% Throttle??? (258 views) (394 thread views) Message:
A couple weeks ago, I was playing around with my OBDII scanner looking at the throttle position readout and noticed when the throttle pedal was on the floor (kick down switch depressed) I was only at 85%, adjusting the throttle cable until I got 100% made a big improvement. Several others on the XJ8/XJR side checked their throttles and noticed the same situation one thoughtful enthusiast Gabriel suggested I share with all Jaguar lovers. Attached is the link to my original post.

Cheers,
Adrian 2000 XJR


http://forums.roadfly.com/forums/jag...9476089-1.html
Link:
http://forums.roadfly.com/forums/jag...9476089-1.html
Best, DaleD

 

Great memory Dale, it was a good read. I've added some quotes from that forum over here, with their respective authors. Thanks for linking this one!

A good project for the weekend. Don't forget to update if anyone does this to their car.

 

This is an interesting discovery and, indeed, with other cars I have owned that had the cable going all the way from the pedal to the throttle (or carburetor), I frequently noticed that there was too much slack sometimes and I would adjust this out. I did not realize this was also the case for drive-by-wire setups and, as always, if someone has some photos along with a good description of the procedure, that would be another great addition to the FAQ section.

Doug

 

I just checked mine, and there was definitely some slack in the cable. The throttle position sensor didn't go all the way to the stop when the pedal was floored. I adjusted it and made a video which I will post shortly. Mine is a 2003 and I think it may be different than earlier years. I didn't see a zip tie or anything. There is an adjustment on the cable and you basically pull off a little clip, slide the cable out, and reinstall the clip. It's hard to explain, but just watch this video:

http://www.youtube.com/watch?v=AV8iF6SMjh8

By the way, the next time I clean my engine compartment I'm going to take off those two covers and clean under them. Forgive me for all of the dirt.

 

OH MY LORD! That's what I'm talkin' about! I just took it for a drive with the newly adjusted throttle cable. I think I added 50 horsepower!

 

Rev Sam: Thanks for the video. I watched and then stepped out to the garage and did the check on my 2005 XKR and sure enough there is about one half inch of travel remaining when the throttle is fully depressed. I will be adjusting shortly.

Are any of the Jag Techs out there familiar with this finding and if so do you have any cogent advice?

Regards

Tim V.

 

On mine it seemed as if some days the car would absolutely haul ***, and other days I would mash the throttle and it would be like "meh...". I think a part of it has to do with temperature. When the car has been sitting in the sun on a hot day the throttle cable will lengthen due to the heat. When the car has been sitting overnight on a cool night, the cable will shrink. My "awesome" driving experiences were probably on cooler days when I first pulled it out of the garage. My "meh" experiences were on super-hot days when the car had been in the sun. I know a hot day can reduce engine power just from the heat, but I'm sure the cable length played a role, too.

Over the weekend I think I'll adjust the cable again after the car has been sitting in the sun for a few hours. Maybe I can pull one more notch out of the cable.

 

That's cool Sam, when I get my XJR back from the detailers I'm going to check it out as well. I have had the exact same thought that on some days the car performs great and others it seems sluggish.

 

Sam thanks for the video It was a great help for those of us with 4.2 litre cars - I was wondering why my XKR seemed to had lost a little life. I did the adjustment and it accelerated like it did when it was new. - The only issue I have now is the fact that pedal is now higher than it was before and does not align with the break pedal. Has anyone else experienced this? Is there an adjustment for the pedals? I'd though i'd ask before I went dash diving bad back and all.

 

My pedal is a fraction of an inch higher, but I drive several different cars so I have to get used to the pedal placement each time I switch. The change in pedal position was barely noticeable to me. How many notches did you move the cable?

 

I moved approx. 4 notches, I tried to remove all the play I could. After the last post I moved it back a notch which helped with the pedal alignment but it lost some throttle response. I guess I will adapt to the new pedal position because the response make a noticeable difference. Thanks again for the video - it made it super simple - Thank Megan for me too.

 

I couldn't wait to get the car home after work and do this adjustment, thanks Sam for being the first to do it on here and showing us the correct procedure!

I'm more scientific about it, and can give you some actual numbers to quantify the before/after results...I'm amazed. I used my AE software to monitor the pedal position sensor, and the throttle position sensor during the adjustment.

Before
A pic of the throttle body, with the WOT engaged...disappointing indeed.



Here is a screenshot of the pedal/TB sensors, fully depressed w/o WOT engaged




---> WOT engaged ... a measly 79%!




Made the adjustment to the cable, I got 2-1/2, almost three notches out of the cable, and I didn't really pull on it...just till it felt taught.



After
The throttle body visually is open SIGNIFICANTLY more, but how much you ask?



Pedal depressed all the way, but not WOT...yet



---> Now, WOT engaged... WOoooHOOOO...100%



= 21% increased throttle opening!!

Just to check my 'pedal at rest' numbers, I ran the scan without any pedal actuation... all seems well.


As to my pedal position, it seems unchanged from the drivers seat, perhaps you guys went maybe a bit too much on the adjustment? I won't test out the new 'power' until this rain stops. My luck, I'll end up 'on the wrong side of the hedge'.

Someone should tell the S-typers and the XJ owners. (those R guys are going to love this test).

 

I wish I had the AutoEnginuity scan tool to adjust it more precisely but all I can say is this "R guy" is ecstatic. Thanks to all!

 

That's awesome! I didn't look inside the throttle to see where the butterfly valve thingy was, but I'm guessing it was similar to yours as I also got three notches out of the cable. I need to get whatever software that is you are using.

And perhaps this should be added to the FAQs.

 

FWIW, I checked my car (with the earlier cable setup) and the setting was perfect from the factory.

 

I guess I should have removed the intake to see the throttle posititon but it is 112 degrees here right now so garage time was kept to a minimum.

 

I don't think I have ever had to occasion to get to WOT. Too many curves/hills.