I've only once gapped the BPR6ES plugs down and it seemed to make no difference whatsoever so I've just left them as they are. If the ignition system is designed for plugs with a 1.1mm gap (as the original recommended Champions had), it shouldn't do any harm at all. I ran a set of the Iridium BPR6EiX for around 40,000 miles up until the engine came out to go to V8 Dev. I didn't have any to put back in and my local factor has to order them in for me but keeps the nickel ones on the shelf, so at £1.99 each, I've been using them ever since. At least with changing them every 10,000 miles, there's less chance of them seizing in.

I've always gapped them down to give the coil/coils an easier time with LPG. I guess it depends on how much zip the system has spare.

She's been running fine on short trips since the Spark Plug debacle, but heading up the A19 tonight she started misfiring and feeling very rough.
My first thought was "Oh God, I've killed the cylinder with swarf from cutting the thread".
I couldn't get the Nanocom to connect either so I was filled with woe for another hour and a half until I decide to pull over again and give the Nano another go. This time it hooked up (I think I'd chosen the wrong vehicle or something) and showed me loads of multicylinder misfires, adaptation errors, and more interestingly misfires on pot 4.
The one I F"£$%D up was pot 6 on the other head (and the spark plug is still hanging in there) so I'm hoping this is unrelated.

Is it fair to assume that the first thing to do with a single cylinder misfire is to check the plug/wire for that pot? I think it's time to get the correct 14mm plugs and swap the rest over. My working theory is that cylinder 4 was misfiring enough to affect the reading from the O2 sensor which leaned out the rest of the engine. I'm hoping it's just an ancient old plug and not my cack-handedness that has trashed the whole engine :(

FWIW, idles sounds OK. Light throttle also OK so I cruise can at 70 on the flat but as soon as we start going uphill you can feel the engine "hunting" slightly and a lack of power.

When I originally got the Disco (brought as spares or repairs off ebay without viewing first) it did have misfiring as the reason for sale. The previous owner had tried replacing the spark plugs and come to the conclusion it probabbly wanted a set of spark plug leads and I suspect felt out of his depth. I drove it back from the outskirts of Gloucester to Milton Keynes and it was fine as long as you didn't give it too much throttle though clearly something was wrong very much like what you describe. That turned out to be mostly his half-assed attempt at changing the plugs as 3 of them were so loose you could move them with your fingers, I replaced the leads at the same time as I didn't like the look of them at the same time, though suspect very little was actually wrong with them then.

If you suspect 1 lead is going bad, your best to change the lot. 1 cylinder logging misfires would suggest its more likely the plug or lead than the coil pack etc - these usually fail on a pair of cylinders, if you look at the diagram the top pair of the coil is one pair, the bottom two is another pair and so on. So if you had 2 on the same side of a single coil pack, it would suggest the coil is at fault (I'd suspect a damaged plug or shorted lead might cause the same result though as it would short circuit the good plug on that one).

Also changing the rest of the plugs given you know they are ancient would be a good plan, Might also be worth resetting the adaptives and seeing what your then left with, given the other logged errors. Once you've done that, have a look what the trims look like with the Nano would be the next step just in case something else is wrong (vacuum leak for example might explain some of the symptoms, particually if its not constant - something like a pipe rubbing against something so its only leaking some of the time)

Thanks! I needed some validation before I pushed the PayPal button again....
I think this is going to the garage, it's too dark, cold and wet outside to be arseing around with a headtorch. They can take the risk on the 6 remaining oversize plugs too!

Best hope Simon doesn't see you say that, he will be calling you a Nesh

Anyone can be uncomfortable! :)

To be fair... I'm probably going to get a garage to look at the clanging noise that I'm pretty sure is coming from the drive shaft on my BMW, because its dark and cold in the evenings, and I hate lifting up "normal" cars at the best of times. Let alone dropping the exhaust, heat shields and prop shaft out...

Sometimes its less faff to make it someone else's problem! :)

Hehe that's true Bri!

Morat wrote:

Anyone can be uncomfortable! :)

Nesh bugger Miles! ;-) I prefer to work outside on cars and do so whatever the weather. There has to be a foot of snow before I think about working inside, when it's dark (nearly half my hours at work these days) I use work lights, I'd use work lights inside anyway. Boots, longjohns, thermal shirt, shirt, coat and Russian looking head warmer on today (not jumper weather yet lol) and I've been sweating. The birds/doves in the yard are so used to me being there they'll sometimes come and land on the ledge of an open car bonnet while I'm working on the engine hehe.

work lights would be handy, no doubt! tbh, I'm at the age now when I want them during the summer too!

OK, I got all the old wires out and 6 new Platinum NGK 14mm plugs in before having to leave for lunch.
All the old wires have crappy corroded conductors/connectors at the plug end. Some of them were welded to the plug and I just pulled the wire out and had to put the spanner over the remaining rubber.
Is there any magic potion I should apply before ignoring the whole lot for another five years? :)

I went with platinum in the end as Iridium are just too spendy, I may regret that one day :/

Dielectric grease is sometimes recommended, though I've never bothered. Couple of times I've found white deposits in the plug leads. Some leads I've fitted have come with a tiny sachet of grease. I think the idea is you apply it to provide a barrier though its never been very clear which bit you should be applying it to. If you got 5 years out of them, I'd think you were doing ok personally.

I put a smear of the red raspberry jam brake seal grease (the stuff we all have a 30+ year old tin of) on the inside of the boots on the plug leads. That way they don't stick to the plugs and you can get them off when the time comes.

5 years is what I'm hoping for :)
Marty says he swapped the leads for me a couple of years back but I don't remember and it's not on my list so they probably pre-date my ownership.

The plugs are OK once I've got them out with a decent gap and light, light brown deposits but the outside of them is rough. There's rust on the hex and conductors and the wires are all grim on the inside of the connectors which seems to be what caused the misfires/weak spark. No4 was badly corroded.

I've bought some silicon dielectric grease just for the hell of it. I'll smear some on the plugs when it arrives - hopefully it'll help seal the boots up and prevent corrosion. If not, it'll save my knuckles when I pull the wires off next time!