road speed transducer

hi guys i have a 3.9 v8 auto discovery engine that is in a defender 110 crew cab it has idle issues where it revs up and down when stationary.
I have been told to check the RST but i dont know where to start looking if you guys could help please thanks in advance.
rob

little box on the chassis rail by the gearbox usually

Unlikely to be the transducer, if it is a hotwire injection system, the transducer only sends a signal to tell the ECU to switch on or off the idle stabilisation. Where your idle is irratic I would suggest starting with cleaning the stepper and plenum, check and set the throttle disc and make sure there are no air leaks on the induction system.

hi yea i have cleaned the stepper and the plenum and resealed with hylomar i have checked the air gap and that is fine i now have the problem of not running all 8 cylinders i have just swapped the rotor arm dizzy cap plugs and leads it runs like a bag o ****e at the moment.
next i think i will reset the base idle

use gen parts and or magnecore leads.

pattern are ****e!

disco300tdi said:

hi yea i have cleaned the stepper and the plenum and resealed with hylomar i have checked the air gap and that is fine i now have the problem of not running all 8 cylinders i have just swapped the rotor arm dizzy cap plugs and leads it runs like a bag o ****e at the moment.
next i think i will reset the base idle

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Make sure the HT leads are correctly routed and properly clipped. As Fett said DO NOT USE pattern parts in your ignition system - that means Lucas Cap and Arm and any good quality leads. You might also want to check some other things while you're in there. Are you getting a big fat spark off the king lead?

As above, I binned the RST on my 3.9 and it runs fine.

check the ingition timing.

remove all leads and get a spare plug and check each one to make sure there is a spark at each lead.

and yeah, pattern parts are a gamble at best, dingocroft.com famousfour.com do the genuine lucas.

when my road speed transducer has a broken wire inside it, the car ran perfectly but when i slowed down to traffic lights it used to cut out. having said that, the 3.9 doesnt have a speedo cable normally - has it got a cable and RST, or just an electric speed sensor?

if its a speed sensor, does the speedo work too?

i am sure it has a speed sensor and the speedo works fine too gotta have a look tomorrow the rotor arm is a **itpart i have just noticed damn

put that straight in the bin then!

yea will order lucas one tomorrow lol

try and get the silcon coated one, it really makes a differnce on the cold damp mornings!