well its okay thanks for the heads up though i was about to take the whole engine apart just to find the cable =) LOL JK

 

Wow - I've been trying to figure out where this adjustment is from just reading about it with no success. Thanks for the video, Rev. At least I know where to look now.

 

Just made the adjustment on my 2006. Took up 3 notches on the spindle and I can't believe the difference. Now I know why my wife's 2005 XJ8L was blowing my doors off. No more - I'm guessing they are about equal now, but then hers is aluminum.

 

I always thought that the slow throttle responsiveness on my 2001 XKR was due to the throttle body being dirty or something. Well today I decided to make change to my throttle cable. After removing the zip tie I popped the square off the bracket turned one turn counterclockwise and inserted the square back into the bracket and attached a new zip tie. I started the car and took it out for a drive and was amazed at the difference. Gone was the slack in the pedal at very low speed, instead the car was immediately very responsive. It definately solved the problem I had with the car since I purchased it in 2008. Now I am kicking my self for not doing the job sooner. At first I thought the change had raised the RPM, but after the car was warmed up it settle down to the normal 600 rpm at idle range. If I can do this job trust me anyone can. You won't be dissappointed.

 

what took you so long john?

 

Nothing more than the belief: "If it ain't broke don't fix it". But all the comments about the change in performance got the best of me and gave me the confidence to do it. I did read all the threads about making the change and it sounded very simple and was.

 

I had read about this fix, but did not know where to look. I searced for a cable at the trottle body, but (obviously) to no avail. I just assumed that they had changed the configuration sometime before 2006. Then I saw the link to Rev Sam's video and watched it just out of curiosity. AHA! So that's where they hid the cable and its adjuster. The rest is history. What baffles me is how something so simple-but-significant could be such a long-term, universal problem without Jaguar having fixed it somewhere along the line. Oh well: Long live the Forum!

 

There is really not a defect or even a "universal problem" but, rather, merely an adjustment that should be checked every so often. Even going back to cars I have owned with carburetors, there have been routine adjustment needed for not only the cable from the pedal to the carb but also the rod that controls kickdown of the automatic trans. The perceived improvement in performance from adjusting the cable so that the throttle body opens quicker given pedal movement is just that--perceived. Of course if the cable was so out of whack that the throttle was opening only about 80% when floored and now it opens 100%, then you have gained back what should have been there in the first place. Adjusting the cable did not magically give the engine any more power--you are now just engaging the power that was already there.

Doug

 

True, same principal as the parking brake cable. Mine had stretched to the point that I had to turn the adjuster three turns to set it properly. A real improvement!

 

Sorry if I seem to be but it is misleading to represent this adjustment as some type of miracle performance modification.

Doug

 

Never said it was a modification. Just an adjustment just like the brake cable I adjusted. It wouldn't hold the car very well and I had to pull it up all the way. A little adjustment and the parking brake functions as it should.

 

Doug, every time I read a post from you on this subject, you do give the impression that there is not really any improvement, only a 'sense' of improvement (by the definition of perceived I suppose) You do explain it well when you describe the adjustment as 'returning the TB response and operation to original parameters' but for some reason, the perceived thing always gets to me. Anyway, I think everyone gets the idea.

 

Yeah--I guess I can be a royal pain-in-the-a** but it is probably because I am an engineer. For some reason it just irked me that this adjustment was being touted as some magical performance modification. Folks were getting all excited about the fact that pushing the pedal further results in more power.

Doug

 

Yes.....I would concur with that !

 

Actually, I get excited about the fact that pushing the pedal the same distance results in more power. Prior to the adjustment my engine would not develop full power. Now it does. That's something to get excited about!

 

To what do you concur--my being a pita or celebrating the fact that opening the throttle blade more results in more power?

Doug

 

I appreciate all of you points, Doug, and certainly agree that this adjustment is not creating any new power, just reclaiming responsiveness and possibly some power that is already available. In my case, I do believe I was not getting full open throttle, and I took in at least 3 and possibly 4 notches on the adjusting spindle. I gotta say that it still seems odd to me that a car that is only 4 years old with under 20,000 miles would be that far out of adjustment. Anyway, I sure am pleased with the results.

Regards -

 

You are correct about it being peculiar that so many of our cars are incorrectly adjusted in terms of the throttle cable (this seems borne out by the number of folks here that found this problem). I guess these cables stretch over time and/or bumps and vibrations from daily driving throws the adjustment out of whack. Then again, this explains why the cable is adjustable and why there is a written procedure in the JTIS for periodic adjustment.

There was a virtually identical thread to this one over on the Corvette forum. One guy discovered the gizmo to adjust the throttle cable on the C4-vintage models and there were bunches of guys who discovered that there was way too much slack (throttle blade was only opening 80% when pedal was floored) but that this could easily be adjusted out. In some cases, the owner overdid it and ended up with the car idling at 2000rpm. However, due to the self-correcting nature of this gizmo (I suspect similar to what we have on the Jaguar), pushing the pedal to the floor would re-adjust the cable to the proper length.

Seems to be a common issue with newer cars that have throttle position sensors.

Doug

 

It doesn't seem to work like that on my 1971 Corvette LT-1 (C3). Goes something like this: Mash the gas pedal, Mr Holley opens all four barrells, raw fuel pours into engine, a few seconds of noisy exhilaration, stop at next gas station.

 

Ah yes--those were the days!

Doug