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barker746

New Member

• Aug 1, 2010

• #1

hello peeps, my 97 v8 auto 3.9 disco tickover is 900 rpm in neutral, in gear driving round town i end up riding the brakes cos idle speed now at 1250 rpm . anyone know how to bring the tickover down as i cant see any way of doing it . cheers steve

 

discool

Well-Known Member

• Aug 1, 2010

• #2

Your tickover is controlled by your engine management ecu. But have you tried cleaning the idle control valve aka stepper motor positioned at the rear or the plenum chamber.

 

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barker746

New Member

• Aug 1, 2010

• #3

the ecu has been replaced with one from a 95 v8 3.9 es after both heads had to come off + be skimmed my old ecu decided to retire itself . where would i find the plenum chamber + the stepper motor? cheers steve

 

discool

Well-Known Member

• Aug 1, 2010

• #4

The Plenum its the alloy top with 3.9 on it and the idle control valve is at the rear with the blue & orange wires, so unplug and unbolt it and spray the working parts with brake cleaner and put back carefully.

 

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Last edited: Aug 1, 2010

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barker746

New Member

• Aug 1, 2010

• #5

many thanks i,ll give that a try + let you know what happens

 

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barker746

New Member

• Aug 2, 2010

• #6

i,ve stripped the idle control valve out+cleaned it as per instructions(boy was it dirty), no different to tickover . anything else i should look at?,cheers steve

 

discool

Well-Known Member

• Aug 2, 2010

• #7

Ok still keeping it simple, is your air filter clean? also look for any air leaks, splits in hose's going to the plenum, hose clip joints, also the seam that goes around it where the top meet the bottom and also the large AFM hose. Any additional air leaking in will upset the tickover.
After that you will be looking a faulty items like the air flow meter AFM that's the lump just after the airfilter, you should get the engine pluged into the diagnostic kit (testbook of similar) to confirm.

If you also post in the it's a V8 mate, engines forum u may get a few more responces and may get it sorted for u

 

Last edited: Aug 2, 2010

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barker746

New Member

• Aug 2, 2010

• #8

all hoses are okay replaced some iffy looking jubilee clips . air filter is a cone shaped k+n one cos the lpg regulater sits where the air box use to . idle the same on lpg or petrol . the seam of the plenum ok . will have to get it plugged in , thanks for your input , cheers steve