Plugs

[Merlin]

Have just got a box of NGK - BPR6ES spark plugs.  Are these GOOD for a 3.9efi engine?
PS-No snow here, not a cloud in the sky, cold though.
Cogs

[hobbit]

According to my oracle
Champion RN11YCC
Autolite APP64
Beru 14-8DU
Bosch W8dc
Champion RN11YCC
NGK BPR6E-VG

Are whats listed, but I dont believe these are the only ones, so sorry not much use to you, some times the lists are only the recommended ones, but not necessarily the compatible ones

[Range Rover Blues]

BPR6ES should be fine, I had a set of BP6ES untill recently, they were recomended for the 3.9 running on autogas particularly and have been good (although our car doesn't run too well on petrol, whatever plugs I fit).

I prefer not to fit resisted plugs to the Rover V8 but it makes little difference on Petrol.

The plugs I am not running are grade 7 Iridium that I bought from Chris Pefect. (BPR7EIR or something).

Hope this helps

[Merlin]

Thanks for the info. folks, I have an occasional "fluffyness" when warmed up, not a mis-fire as such but is proving a bug--r to find. Wouldn't want to fit a new set of the wrong plugs in case it made matters worse.  Will fit tomorrow if weather permits & keep you posted.--Cogs

[Merlin]

Now where to go !!!, New plug leads (genuine parts), NEW plugs(as above),NEW dizzy cap(Genuine part)-it was TWICE as dear as a Britpart one & we couldn't see ANY differences.
Still got my mis-fire when warmed up & under power.
Am going to take it into my local independant L/R place next week as Iv'e run out of idea's what to do/try.-GRRRRR :(  :(  :( -£££££!!-Cogs

[Range Rover Blues]

Firstly do a compression test!
Run some injector cleaner through the engine, this takes a couple of tankfulls!
Does it use any fluids?
Were any of the plugs mis-coloured or different from the others when you took them out?
Does it run like a cow if you disconnect the temp sender for the ECU? (ECU should think the engine is cold and 'choke' the engine).
Have you got the Haynes manual and a multi-meter?  If so you can do a basic check on the EFi system to make sure none of the sensors are toast.

Is the coil ok?

[muddyweb]

Check the fuel filter too if it hasn't been done for a while.

[Range Rover Blues]

Check the fuel filter too if it hasn't been done for a while.

Oh yes, forgot that one.

[coffee boy]

cogs i had a simaler fluffy missfire on a 44k 3.9 it eventually got the better of me 1 day when i came 2 go to work and it wouldnt turn over, 1 cracked cylinder liner 1 more than useless v8 . hope its not the same on yrs!!!!!!!!!!!!!!!!!!!

[Range Rover Blues]

And that is why I asked if you were using any fluids.  The later, larger v8s have something of a reputation for splitting around the cylinder liners, but the problem tends to show up just after you switch off, when the cylinder pressure isn't there to stop the coolant leaking over the top of the liner.  The very late models engines didn't have liners, which is how they got away with such a large overbore.

Apparently one tell-tale sign is a very clean combustion chamber, the leaking collant steam cleans the engine, you have to take the head off to see it though!

anyway, DON'T PANIC.  There are dozens of quite tedious little things that could, and probably have, gone wrong with the EFi system, whether electrical or fuel related, so start there.

[Merlin]

Got that info.  Now got a new "Fuel-Filter" fitted, no change :(  so will work through the rest of the suggestions & keep you posted re-sucesses/faileurs.--Cogs

[Range Rover Blues]

Best of luck!