What does it do ??

[burgerman]

 Got a 1991 V8 3.5 efi disco
    @ the back of the plenum chamber/next to the bulk head there is a sender? with a few wires going into it, -  -  -  What does it do/called  :-k

 I ask cause i am having overfueling/running very rich issues with her, have replaced plugs/leads/cap ect- also airflow meter still got a big hiccup coming off idle, and often if stalled off roading wont restart with out a tow, then chugs out black/fuellly smoke out

  Cheers for any tips/advise

[Range Rover Blues]

That's the idel bypass stepper motor.  With some of the problems you describe it could be toast.

[burgerman]

 sounds likely to me, I reckon Pt no    ETC6660  Anyone got one spare ??

 Many thanks

[Rossko]

Don't change that, all it does is control air to adjust idle speed.  It can stick and give you idle too high or too low, but it can't make it run rich.

Checkout temperature sender (not the same one as works the dash gauge), and the vacuum pipe to the fuel pressure regulator.

cheers, Ross K