I had adjusted the throttle cable on a 2005 xk8 and was thrilled with the pedal position in relationship to the kick down of the trans. I later on found that my fluid level was @ 16oz low and corrected that issue. Today I drove the car for the first time since the fluid level adjustment and found that I couldn't get the previous kick down at various pedal positions that I obtained prior to the fluid level adjustment. I pulled over and adjusted the throttle cable a bit tighter and over did it a bit but I was once again able to achieve the kick downs that so delight.
Since nothing else changed I'm a bit confused as my mind suggests that low fluid level would lead to just the opposite result.
Please answer so I can sleep better this evening.
Thank you


wj

 

What fluid level? Engine oil? I wouldn't think 1/2 a quart would have any effect on the throttle response.

My guess is the cable adjustment you made wasn't quite right and you fixed it the 2nd time. Maybe the throttle wasn't opening all the way with the first pass.

Either way, sounds like you are good to go now.

 

maybe this clears things up
1 = oldest
7= newest



I'll try to fine tune the adjustment but I'm looking for an explanation.


wj

 

How did you find this out?

When this transmission was refilled initially (Mercon SP), was it done correctly, with the temperature-based, engine running method? If it was initially filled correctly, is there a leak explaining the lower level later? I am trying to figure out the history and the "data". Thanks.

 

I personally did both fills and the 1st time I didn't get the filler capped until I was reading 51C.
The second time was done with less drama...please accept that the information I just gave is accurate.

wj

 

When I adjusted the gas pedal cable a while back, I remember that the adjustment "tab" locking the cable in place was not a complete positive engagement, i.e. it does not completely lock the cable in that position. I took it to be designed that way so that the cable could be put in "too tight" initially, then, when the pedal is pressed all the way to the floor, it is meant to snap back to the proper position, essentially loosening the adjustment. I would not recommend adjusting it that way, though, on an aging car.

Did you have it too tight initially, and never really put your foot to the floor (engine off)? If you did, and pressed to the floor later (even with engine off), that adjustment may have snapped back without your knowledge.

I believe this adjustment is meant to take the slack off of the cable, not to put any pre-load.

Separately, I read (but I am not positive it actually does anything) that after a (mechanical) cable adjustment, you are supposed to "teach" the computer about the sensor range, and slowly put your pedal to the floor, hold it there, then release slowly, all of this with key on, engine off.

Last, just to state the obvious, the final answer is digital. That cable goes to a sensor (throttle by wire), and the live sensor value should be readable over CAN (you might need the factory software for this, though, not positive it is available over OBDII). Separately, the throttle position is also a key piece of data in this whole scheme. The proper adjustment is when you can obtain 100% throttle opening with the gas pedal. If you were to put your foot on the floor, and somehow not get 100% throttle opening, then the adjustment is too loose and you are "loosing" power.

Best of luck, keep us posted.

 

Hi,
Thanks for that info.
Before diving into all of the various scenarios let me make this statement. No one else touched the car from the time I drove it with the lower fluid level and ‘great’ throttle/kickdown response until this minute.
After the fluid add I drove it in the exact same manner that I had previously, after the car was warmed up I wanted to experience the smooth strong pull of the engine. I noticed that the kick down I was so enthralled with no longer existed. At that point I started experimenting with various road speeds and throttle positions…after @ 40 miles of that I concluded that the cable must have ‘slipped’ the collar. I popped the hood and inspected the cable, it was secure and as before. I then pulled it one ring tighter even though there was no slack present. This did change the kick down behavior for the better but it was not correct as it seemed to force a shift into one gear too low.
The only variable was the addition of fluid…it somehow had an effect on the shifting.

wj

 

FOUND!!!!
I discovered the cause of my dilemma...either I unintentionally pressed the 'S' button, or it lost its setting when the battery had been disconnected. Whichever, the transmission now downshifts as before.

 

When draining and refilling a transmission you should go back after a few hundred miles and check the fluid level again. Reason is depending on the time draining air pockets can exist and your driving the car can dispel the air causing the level of the fluid to go low.

As for the shifting pattern after the change of the throttle body cable that could be explained. In short the transmission control module is taking information from the engine control module to tell the valvebody in the transmission what to do. If the load request from the engine is high it will down shift if it is low it might think about shifting and a simple cable adjustment could cause this to take place. You should also consider your doing a hard reset will clear the engine control module changing what it saw as the norm.