Hi all, I have just replaced the transmission kickdown switch on my 1984 xj6 series III, as the one on it is cracked and missing a terminal, it had only two terminals, the wires are there but it was not connected at all, so i purchased one that looks exactly the same and fitted it and connected the wires and very excitedly started the car for a test drive and it coughed and spluttered and would die in revs at about 1500 rpms, I disconnect the wires and its fine, then adjusted the position of the switch connected the wires and same again?
any ideas on what is causing this? thanks in advance

 

I suspect what you replaced isn't the kick down switch.

Where is it located?

Is yours a fuel injected 4.2 or the 3.4 running on carburettors?

Some fuel injected 4.2 cars had a lever-action fueling switch in the throttle linkage, as well as a rotary action fueling switch as the bottom of the throttle body which served different functions depending what market the car was configured for.

Cheers
DD

 

Hi Doug,
Hi Doug its the switch in the switch in the centre of the pic on the throttle linkage just above the intake elbow.

 

I'm a bit foggy on non-USA spec cars but I'm pretty sure that's a fuel cut-off switch.

When coasting with the throttle is closed ("over run" situation, very high vacuum) the fuel injectors are cut off until the engine drops to about 1400-1500 RPM.

That's about all I can remember at the moment. I'll try to do more research later if nobody else chimes in with more/better info

Cheers
DD

 

Thanks Doug, as you might have guessed I am learning my way around this car, what I ordered was listed as a transmission kickdown switch and looks very much the same as what was there, when I googled thats pretty much the same image that came up, but you might be right, if i can find a manual or check where the wires go to might explain.

 

The same switch was used by Jaguar for many years and a variety of functions. Somewhere along the line, decades ago, it must've been cataloged as a "kick down switch" and the name followed the part no matter where or how it was used on the car.

Cheers
DD

 

I can confirm that the switch in question is a fuel cutoff switch and is used to cut off the fuel supply when the throttle is shut above a certain revs value. When the revs drop below the defined value, fuelling resumes. The switch is on an adjustable mounting and must only be open when the throttle is close, so one loosens off the mounting screws and, with the throttle closed, adjusts until an audible click is heard telling you the switch is open.

Read here on Throttle Switch: -
Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering

 

Thanks Doug and Fraser for clarifying the switch and thanks Fraser for instructions on how to set it.