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Kickdown - Sometimes It Does, Sometimes It Doesnt

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Hi All,

Went for a drive this evening to get some shopping from supermarket (what an exciting life i lead!)

On the way there i was coming off a slip road onto the dual carraige way. Floored the loud pedal expecting the usual satisfying surge of acceleration, and nothing! the car didnt speed up. Tried again pushing the pedal to the floor and still nothing! Occured to me after a while that the kickdown didnt seem to be working. No matter how hard i pushed the pedal at low revs the box wouldnt change down.

Got to supermarket, did shopping, started drive home. Floored it, the box changed down fine and acceleration was good again! Tried this a number of times on way home and it was fine.

So- sometimes the kickdown works, sometimes it doesnt. If its not working sometimes when i stop the engine and start it again it will work. What could the problem be? is there some sort of throttle sensor that controls kickdown that could be faulty? could it be an internal gearbox problem? is there a gearbox ECU that could be faulty. Please help?? its a 1991 LS400.

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Were you trying the kickdown at the same speed as when it was working?

There is a sort of area in the rev/speed range where it will not kickdown.

Eg...Say from standstill and you floor the throttle pressing to the floor so its in kickdown the gearbox will change up at max revs in that gear say 50mph it will change up into second gear.

Lets say your driving at a steady 30mph and use the kickdown it will change down to first gear.

Lets say your driving at 40mph and use the kickdown you will find it will only change down to second gear and car feels as sluggish.

Anyway,the first thing id do if i owned your car would be to do a ECU reset,theres posts on here of different ways of doing it.

The other thing id do is check that the carpet/mat in the drivers footwell is not getting in the way of the switch when you floor the throttle.

Hope thats of some help.


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I believe that LS's have an adaptive ECU, in that it will learn your style and manner of driving, possibly not reacting to anything unusual.

There are posts on this site to get over this by either resetting the ECU, or giving the old girls a good thrashing, so that their ECU's get used to another style of driving.

Me, I'm a dawdler, preferring to experience the luxury without fretting.



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