Idle Problem

JMAN as far as I am aware the way the stepper works is that when you switch off the ignition the stepper tries to wind itself out more steps then it can do. This is to ensure that no matter what position it is in when you shut the engine off, the motor will wind itself all the way to the park position.

So since you pulled it out when it was shut down, it was already in the park position. So giving and removing power again without starting the engine will leave it in the park position and then it will try and wind itself back to the park position.
I don't think I've explained it particularly well but I'd say your stepper is fine.

To test it this might work. Start engine and disconnect stepper when idling. Stop engine and remove stepper from engine. Then turn the ignition on then off. The stepper should be seen to operate. I haven't done this but can't see why it wouldn't work.

I'll give that a shot. cheers!

Just reading thorugh this thread and it looks as though the problem has been solved.
I did have a similar problem with my '96 3.9l, idle in drive was all over the place, but was OK in neutral or park, so problem was when engine was 'loaded'.
Replacing the stepper motor helped for about a day then it went back to its old tricks.
So I replaced all ignition leads, new dizzy head, rotor and a new set of spark plugs and that did solve my problem.
It now idles in D in the 650 region with a bit of variation which is to be expected.
However, I still have another problem with starting the engine after it has reached operating temp, I have started a new thread on this, so any help would be greatly appreciated, thanks! :)

just had my stepper changed and got rid of the bouncing idle but now mine seems to idle at about 1500rpm after driving around for a while,its normal when i start up.

My Discovery 1 has been stalling on occassion and I hve been unable to find the problem. It only stalls when the engine is warmed up and sometimes the engine hunts from almost no revs to 1500 rpm. I have replaced the fuel pump and air flow meter, but have now been told that the TPS is suspect.
Any ideas? Where can I buy a TPS in South Africa. The LR dealers are very expensive. The numbers on the unit is 215sa and 70408 A.

I was helping a guy in Sweden or somewhere to install a14CUX on an old RR on another forum.
He had this irregular idle problem and it turned out ot be the vacuum advance Diaphragm was split giving an air leak.

Before buying a new TPS, you should test it.There are three wires . one is earth , one 5V and one the return to the ECU. I have forgotten the colours buy easy to tell as one is zero volts, one five and the one you want is about 0.4V at no throttle.
Get a multimeter , preferably the now non existent analogue type and slowly move the throttle open, the voltage should smoothly move from 0.4 or whatever to around 4.5 or so. The important part is that voltage does not drop at any time.
A TPS typical fault does not usually involve idle but the move FROM idle, as they usually wear just off idle, ie where you have your fooT on the throttle most of the time. They ar elike a volume control on an old radio
ie a variable resistor.
Regards Philip A

May I suggest you also check the 3 pin plug/fly lead to the TPS hidden under the Throttle Body & give it a good clean.

Slurpie, buy from UK - Craddock, Paddock, Rimmer, Island.

HTH

Pete