rough idle causes?

rangerover8 said:

thanks claasic kev , will get on this tommorw asap. When u say everything as it should be do you mean , dizzy cap rotor arm spark plugs etc etc , should i only clean plenum and ram housing as a last resort?

Yes and no. Clean the plenum and ram housing in any event.

should i be checking the simple things first? e.g spark plugs dizzy cap? even tho it runs ok on the lpg? Yes.

It wont idle at all, when started on petrol it more or less just dies instantly and if it does idle it sounds very ruff like a misfire .

Check the throttle potentiometer, if the base voltage is wrong the ECU won't activate idle stabilisation.

the other night i took it out for a drive, i let it run on lpg until warm, then switched to petrol idle was a little ruff , but then pulled up to next set of traffic lights and the idle was spot on , turned the range rover off , then tryed starting it again instanly on petrol and it wouldnt start and when it did was back to being ruff idle/ coughing spluttering etc. weird as it was running great no more than 30 seconds ago.

Sorry for this as iam not that great mechanicaly minded but willing to give anything ago. just really want to get to bottom of this Thanks for the advice so far.

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classic kev said:

Forget the air flow meter it isn't your problem!

The problem is a lack of smooth stable idle. Even with the MAF disconnected the engine should still idle, it will run extremely rich but it will still idle and run O.K. trust me on that. (If everything else is as it should be.)

Clean your plenum and ram housing!! Maybe get busy with the multimeter and check throttle pot and coolant thermistor.

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rangerover8 said:

i notice that my vacumn advance going to distributor hose is not in good shape ,so iam sure that wont be helping things. What happenes if this is not connected correctly?

i have the lpg side of things working again its all good.

Just the petrol side wont idle at all now it just dies and even with foot on acclerator it gradually dies.

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