Rough running, black plugs...Disco 3.9 V8

[JimsMowing]

Hi guys. I have recently bought a Disco 3.9 V8 with lpg. Everything has been running great and i couldnt expect anything more! Its awesome and i love it.

However i have been through a few muddy fields with some very tame off-roading and i thought it be best to clean it so corrosion wont start to form. So yesterday i took it to my local sainsburys and gave it the premium wash which included the underchassis bit which i thought was a touch as it means in areas i cant get to it would.

MISTAKE no 1.

I had the engine running at the time of the wash, and as soon as it finished i noticed a slight hesitation in idle. I got out had a listen to the exhaust note, and it was uneven, and a bit spluttery. B#ll#x i thought, it must have got some damp into the distributor cap. No worries i'll sort that out when i get home. Get home check it out, its bone dry. i clean the very small crap off the points and put it back  (it looks brand new).

Start it up, engine cool now. Let it idle, take it round the block come back and its running rough again.

So i check the plugs (one from each bank) and they are black. Now as it has lpg and petrol, i dont know what to do to get this issue sorted. It is virtually out of gas, but im running it on petrol now so i thought that wouldnt have anything to do with it.

If anyone has any suggestions i would be eternally grateful if they could let me know.

Kind regards

Geoff.

[gtomo2]

sound like its been set up to run on lpg. mine is a 3.5 v8 and runs on lpg and petrol. And that is tuned to run on lpg so its a bit rich on petrol. think the diffarance is something like petrol timing 8 deg btdc and gas is 12 deg btdc. hope that info is ok for you

[JimsMowing]

Cheers for that info. The thing is up until i went into that car wash it was running great, so i can only assume that it has had some sort of effect on it.

Other than what you had suggested, can you advise any places to check?

[Range Rover Blues]

Timing is a bit of an issue, I advise leave well alone if you want to run on both fuels.  Now LPG burns hotter than petrol so some folks fit a cooler plug, that can mean it fouls up on petrol.  On a HC I like to use BP6ES and don't have trouble.

You might also have screwed up a sensor, like a MAF sensor or lambda sensor.  Also check the condition and routing of your leads, no.s 5 and 7 must be separated to prevent cross-arcing!

Oh, and I drowned ours and it started miss-firing, the coil had gone :? figure that one out.

[JimsMowing]

Cheers for that! i think you may have given me some good areas to go over. Particularly the lamda sensor and coil, as the cap to the coil doesnt really fit it properly, and i remember the spray of the jets coming out of the front of the disco at a 45 degree angle so could well have done something to it..

Anyway cheers.

I'll let you know how things turn out.

Geoff

[Range Rover Blues]

Funny that, every set of leads I've bought, including MAgnecor had the coil lead with too big a boot to fit snugly, order a set for a 3.5 RRC.