piey62 Posted January 19, 2010 Share Posted January 19, 2010 Hi I have a 1995 landrover discovery 3.9 v8i when its warm and i pull up at a junction the tickover drops right down to 500 revs jumps up to about 700 then drop right down it usually stalls and is difficult to start there is allso a rattling noise coming from the cats not there when 1st started any one any ideas thanx Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 20, 2010 Share Posted January 20, 2010 Idle stepper valve - full hotwire EFI diagnostics in the tech archive, also search "stepper", it's been covered many, many times. Quote Link to comment Share on other sites More sharing options...
ThreeSheds Posted January 20, 2010 Share Posted January 20, 2010 Like Fridge said - there really are quite a lot of things that could be causing this and you should probably spend some time looking for similar problems that have been covered before, and have a look at the excellent tech archive article on diagnosing EFI problems. Options include (but are not limited to)air-bypass ("stepper") valve, road speed transducer, fuel pressure and the operation of or wiring to, one or more of the many sensors that feed into the ECU so you really need to adopt a methodical approach or you can end up replacing loads of stuff that you don't need to.. For a technical discussion on the 14CUX (the ECU) and the hotwire system, there is this in-depth article on another site that is worthy of note... If you update your profile with your location you may well get an offer of help too... Roger p.s. Having said all of that - I would check out the road speed transducer and stepper-motor first Quote Link to comment Share on other sites More sharing options...
piey62 Posted January 20, 2010 Author Share Posted January 20, 2010 Idle stepper valve - full hotwire EFI diagnostics in the tech archive, also search "stepper", it's been covered many, many times. thanx will check Quote Link to comment Share on other sites More sharing options...
piey62 Posted January 20, 2010 Author Share Posted January 20, 2010 Idle stepper valve - full hotwire EFI diagnostics in the tech archive, also search "stepper", it's been covered many, many times. nice one Quote Link to comment Share on other sites More sharing options...
iomlt Posted January 20, 2010 Share Posted January 20, 2010 My road speed transducer isnt connected and ticks over lovely I through a 3.9 into a 90 hence not connected. Quote Link to comment Share on other sites More sharing options...
ThreeSheds Posted January 20, 2010 Share Posted January 20, 2010 My road speed transducer isnt connected and ticks over lovely I through a 3.9 into a 90 hence not connected. I agree that it is unlikely to be the transducer, but I have heard of a similar problem that was cured (apparently) by replacing it. It is my understanding that if there is no road speed transducer, or it is disconnected (or the vehicle is stationary so there is no signal from it) then the ECU will 'maintain' the tickover at 720rpm, however if there is an intermittent problem on the transducer's circuit so that the ECU thinks that the vehicle is moving, then it will not. So perhaps it's a possibilitity I thought Quote Link to comment Share on other sites More sharing options...
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