Crappy idle- 3.5 V8i

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3.5disco

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175
My 93 disco cuts out at idle and revs up and down a bit to keep itself going in P. If anything its worse when its warmed up

Checked all the vacuum pipes, nothing lose or split, maf connected up properly. Lubed the throttle links- all looks ok

does this sound like a bad stepper motor?

cheers!
 
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3.5disco said:
My 93 disco cuts out at idle and revs up and down a bit to keep itself going in P. If anything its worse when its warmed up

does this sound like a bad stepper motor?

cheers!
Click to expand...

To the best of my knowledge the 3.5 efi does not have a stepper motor, my 3 RRC's certainly never had.
 
norseman said:
To the best of my knowledge the 3.5 efi does not have a stepper motor, my 3 RRC's certainly never had.
Click to expand...

Sort of. A '93 3.5 Disco definately does have one I think you'll find this is because the injection systems are different. The later 3.5's (as used in the Disco) used Hot Wire fuel injection, the flapper system used in the RRC was slightly different.
 
That's what I thought at first but it does have a stepper (one of those cross-over years??)

Took it out, cleaned a load of black **** off it, screwed it back in and it seems to be alright now

touch wood!!
 
classic kev said:
Sort of. A '93 3.5 Disco definately does have one I think you'll find this is because the injection systems are different. The later 3.5's (as used in the Disco) used Hot Wire fuel injection, the flapper system used in the RRC was slightly different.
Click to expand...

I stand corrected Kev, never owned a Discovery & assumed (I should know better!) the engine would be the same. Sorry for any confusion 'Disco'
 
I got "told" the other day my engine was a 3.9 because the idle control was at the back.

Of course on a 3.9 rangey this is the case, but the 3.5 disco had the later system from the outset.

Cheers :D
 
start with this basic setting test then see what happens
disconnect battery for 1/2 hour to clear faults in ecu.
remove and clean the stepper motor and the housing (don't twist or pull the plunger)
remove and clean out throttle blade housing too
reconnect battery start engine and allow to get to temp.
connect a seperate tacho don't use the rev counter not accurate enough
clamp the pipe at the back of the plenum to the stepper motor housing and the idle should drop if it stalls remove the bung on the top of the throttle housing and turn the allen key anti clock to increase air flow restart and refit clamp base idle should be 520 rpm +/-50 rpm
then slowly undo the clamp and the idle will rise then return to normal 720 if it does happy days if not you have a air leak,or fault tps or afm
 
Cheers mate. Already ordered a new stepper so will see what happens with that first

Ebayed a nice weber carb & offy manifold from a classic rangie I used to have, would have gone a treat on the disco :doh:
 
3.5disco said:
Cheers mate. Already ordered a new stepper so will see what happens with that first

Ebayed a nice weber carb & offy manifold from a classic rangie I used to have, would have gone a treat on the disco :doh:
Click to expand...

just bolting on a new stepper will not cure a idle fault if the setting is corrupted or an air leak
 
it ran fine for a week or two after cleaning the old stepper so I'm hoping it temporarily freed up and just needs changing, fingers crossed!
 
F@**ing ****part!!!! Stepper case cracked and it wasn't even screwed in all way. Bet they won't refund either :mad:

Made of that soft fisher price metal
 
I bought a ****part stepper , didnt even work right out of the box. sent it back to paddocks, got a refund but took some haggleing though.

put some copper grease on the thread when you put it in, may help and also will help it come out next time lol
 
got another new stepper for 16 quid on ebay- the part fits a load of GM cars apparently as well

Sort of tried what voguese39 said (cheers mate), the vacuum pipes are all in bizarrely good nick (must have been changed at some point) so the only leak could be the inlet manifold- which i really f***ing hope it isn't.

Have a feeling it might be the tps/potentiometer
 
they aint too cheap, worked a treat on mine after all else failed to cure my crappy idle.

find a good used one is yer best bet unless you find a GM one. if so let me know :D
 
3.5disco said:
got another new stepper for 16 quid on ebay- the part fits a load of GM cars apparently as well

Sort of tried what voguese39 said (cheers mate), the vacuum pipes are all in bizarrely good nick (must have been changed at some point) so the only leak could be the inlet manifold- which i really f***ing hope it isn't.

Have a feeling it might be the tps/potentiometer
Click to expand...

Have you done the other things suggested? It is important that the plenum and ram housing are clean and properly sealed, equally, the throttle disc needs to be set (I can't rememeber what the clearance is supposed to be but you can look it up).

If you are happy there isn't a fundamental set up issue and the base idle is correct and the engine is happy without idle stabilisation then you need to start looking at what controls the injection system (assuming no ignition problems - check your timing). Start with fuel and coolant thermistors, then Throttle potentiometer (throttle switch or TPS), then AFM. If all seem to test O.K. try a substitute ECU.

One other thing before you start, check your battery and alternator are in good shape. Happy hunting!!
 
Thx kev

new stepper did nothing anyway.

Going to bite the bullet & change the inlet manifold gasket- it does "feel" like air is being sucked in
 
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