Base idle tuning - Disco 1 - V8 3.9L

hi_arshard · Nov 16, 2024

Hello,

It’s a Disco 1 V8 3.9L I am trying to tune up the base idle which is currently slightly more than 1000 RPM.

I am trying to set the idle by blocking the idle bypass hose line both side and tuning the screw on the throttle body butterfly, while tuning the screw I can get the idle down to 500RPM but when connect the idle bypass hose back it’s back to the same position 1000RPM
The target is to get it to 750 to 800 I believe this is the standard.

Appreciate your input

Stanleysteamer · Nov 16, 2024

This is just one of the threads on this that I have found.
Maybe you have already seen it, but it says that the ECU is supposed to do it.

3.9 V8 Idle speed adjustment

Have just replaced the stepper motor, and the coil and amplifier in the Disco, and now want to adjust the idle speed, but the rave manual says plug in Testbook to adjust. Don't have testbook, any other way I can set it?

www.lrukforums.com

sierrafery · Nov 16, 2024

hi_arshard said:
Hello,

It’s a Disco 1 V8 3.9L I am trying to tune up the base idle which is currently slightly more than 1000 RPM.

I am trying to set the idle by blocking the idle bypass hose line both side and tuning the screw on the throttle body butterfly, while tuning the screw I can get the idle down to 500RPM but when connect the idle bypass hose back it’s back to the same position 1000RPM
The target is to get it to 750 to 800 I believe this is the standard.

Appreciate your input

HI, did you clear the fault code after the adjustment? that's what they say it's necessary(around the middle of the page) https://www.actproducts.co.uk/2011/...n-system-–-installation-and-diagnostic-notes/

hi_arshard · Nov 17, 2024

sierrafery said:
HI, did you clear the fault code after the adjustment? that's what they say it's necessary(around the middle of the page) https://www.actproducts.co.uk/2011/lucas-14cux-fuel-injection-system-–-installation-and-diagnostic-notes/

How do I clear it? Rover gauge?
As per the last text 2 weeks ago there was no fully code as per the Rover gauge.

Thanks

sierrafery · Nov 17, 2024

hi_arshard said:
How do I clear it? Rover gauge?
As per the last text 2 weeks ago there was no fully code as per the Rover gauge.

Thanks

If that RG has read/clear codes function then yes.... normally if it ran few minutes with clogged hoses a fault code should have been logged

discool · Nov 17, 2024

hi_arshard said:
Hello,

It’s a Disco 1 V8 3.9L I am trying to tune up the base idle which is currently slightly more than 1000 RPM.

I am trying to set the idle by blocking the idle bypass hose line both side and tuning the screw on the throttle body butterfly, while tuning the screw I can get the idle down to 500RPM but when connect the idle bypass hose back it’s back to the same position 1000RPM
The target is to get it to 750 to 800 I believe this is the standard.

Appreciate your input

It is a symptom of a faulty idle control valve (stuck or sticking)… its another fragile item the V8 has I believe, so, follow the instructions if you wish to remove it.

The idle speed is over 1000 RPM + when first starting from cold but should settle down with in 10 seconds, my disco drops down to the normal 760 it’s a bit higher of course if A/C or the heated screens are switched on. Always be the same since it left the factory.

Base idle tuning - Disco 1 - V8 3.9L

hi_arshard

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Stanleysteamer

Well-Known Member

3.9 V8 Idle speed adjustment

sierrafery

Well-Known Member

hi_arshard

Member

sierrafery

Well-Known Member

discool

Well-Known Member

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