The thread (https://www.jaguarforums.com/forum/x...estored-38663/) that has all the great info and discussion about throttle cable adjustments has gotten quite long and sometimes off-topic, and there's no specific XJ8 instructions (although there are some great photos and an explanation of a 4.0 XK), so I thought I'd put my photos and results in a new thread.

First, I went to take the center panel off under the hood, where the throttle cable adjustment is made, and realized that the plastic clip that holds it down was just sitting in the hole not attached to anything - be careful taking this clip out, they are easy to break.



This is what the cable looks like with the plastic cable tie that you have to cut off to do this procedure -- make sure you have a new one to replace it with!



This is how much slack I had in my cable before starting the adjustment.



The adjustment is done by pulling the square bracket out of the metal holder and turning it counterclockwise which moves the bracket on the cable sheath toward the front of the car. You can see how far I twisted mine -- this was too far since it made my idle go up to 2200 at rest --- I backed it off a couple turns and now it idles at about 600, which is where I like it.



This is how much slack I now have in the cable.



And finally, here it is with the new cable tie -- sorry about the orientation of this photo!



I hope this helps.

 

The results? When I hit the accelerator, it accelerates! Before I did this, there was so much slack that at first you'd wonder if you were actually pushing on the gas pedal. Now it moves when you ask it to.

And, as someone else also mentioned, it downshifts without having to floor it.

The responsiveness of this car has been restored (although I don't know what it was like new, but I'd bet it was a lot like the way I have it now!).

 

I'll add - to confirm this process electronically, using an OBDII reader with the TPS reading function - you're looking for between 95-100% when the throttle pedal is floored.
On R car's this is when touching the kickdown switch, on normally aspirated cars, it's when the pedal hits it's stop.

Also, having cleaned the throttle body and MAF, fitted a new air filter, and adjusted the throttle cable, followed by a hard reset that allows the throttle body and ECU to re-calibrate - should give the 'as new' throttle response, and that's something to enjoy!

 

Thanks Sean! I wish I had an OBDII reader...but for now I'm doing by the seat of my pants, literally! LOL In any event, it's better than it was.

I also cleaned the throttle body and MAF and did a hard reset a couple weeks ago.

Maybe another hard reset is in my car's future.