Hi all, first post so be kind..

Car:- 2001/2 V8 4.0L Disco 2, Australia spec, 100K miles. Note - no engine check light in Aus.

Recently it's developed a random misfire. Sometimes it's perfect, other times runs like a V6. At first I suspected the MAF as that was replaced 3 months by an OEM part (which I now realise might have been a bad idea). Anyway, I got a genuine one and it made no difference. Bugger.

Codes (or not) via Scanguage II.

After more head scratching it turns out cylinders 1 and 6 both have little, if any spark. The other 6 are fine. The car has the original leads which I'm happy to swap but I'm thinking that it might be a coil pack as both 1 and 6 are from the same one. Reasonable assumption? Would that be a common failure mode for a coil pack, i.e, a pair of cylinders at a time and specifically say 1 and 6?

Thanks - FF aka Boz

 

start with new plugs and wires....

 

Yep, it turned out to be 2 faulty leads. The plugs were only 5k old and not the issue as I checked for spark before the plug.

I was lucky enough to score a complete set of guaranteed used genuine leads and coils on ebay for $80 delivered which was great as I could swap leads over to compare etc. Of course the used leads will fail at some point but at least I was able to easily isolate the fault - when you live in Australia LR spares tend to be expensive so I get most of mine shipped from the UK.

Also now I've got a complete set of coils and can visualise them it might be worth experimenting with alternate mountings as the current place is less than ideal... I'm an mechanical & electronics enginner so modifying the harness and making a couple of brackets holds no fears. Probably won't get round to it but it would make so much easier....!!

FF

 

you should really look at 8mm leads as the insulation will hold up better and you wont suffer from misfires.

 

Try premium fuel for starters.

 

I'll get the best leads availably locally. Given the originals lasted 10yrs/100k miles without a single misfire I'm sure that any decent set will do the job but I take the point that 8mm would be nice if available. (update - NGK seems to be the popular choice for replacement leads here - all 4 autoshops I visited quoted them, about $80/set. Not too sure of the diam but the brand is reputable)

I use 95 RON fuel which is the official recommendation for this engine and will stick with that - available grades/ratings here mirror Europe e.g. 91 (mainstream in Aus), 95 (mainstream in Europe) and 98. US ratings follow a different scale but from memory European 95 RON is the rough equivalent of Premium in the US. You can also get e10 here which is effectively a blend of 10% Ethanol and 90% 91 RON. The effective RON is about 93/95 depending upon the brand and the Disco runs fine on it as does my other car, an 06 MX5. e10 is now increasingly replacing 91 RON outside of rural areas.

Than ks for all the help - FF