WHAT MAKES A SPARK PLUG MELT???

[double-6s 0]

hi.

was just wondering what would make a spark plug melt.

have been having all sorts of misfire problems and have today discovered that my new plug in no. 6 is totally fekked - really black and scorched and melted. with only 600o miles on it.

so why would this be? lean / rich??? ecu??? god knows.

anyway, with a new plug in, its running amazingly! torque steer is back which is a sign of lots of power again!

what plugs do other vr owners use??

which is good, as i was starting to narrow it down to oiled-up plugs :(

anyway, any thoughts would be mucho appreciated

[steve_16v 0]

If it's running lean the plugs can melt, I'd keep an eye on it and if the new one starts to go then have a leak down test done to make sure the cylinder/valves aren't knackered.

[double-6s 0]

thanks mate.

can you tell me what mechanical circumstances could do that to the plugs?

ie, could knackered valves, cyclinders, etc do that? or is it an electrical issue?

[steve_16v 0]

Quite a few things can make an engine run lean, it would be worth plugging it into VAGCOM first to see if there are any error codes.

[double-6s 0]

did that today mate.

nothing with engine running or not.

[steve_16v 0]

Probably not a sensor then, don't know a great deal about the VR6 but I'm pretty sure any of the following can make it run lean: dodgy lead, fuel pressure regulator, fuel pump, fouled injector, crap fuel, slight fuel line leak ... and no doubt other stuff I can't think of at the moment. Most likely a dirty injector though.

 

Or if you're lucky the plug gap may have been set incorrectly and caused it to melt.

[double-6s 0]

injector was mentioned today. gonna try a can of injector cleaner just in case its just blocked.

[Kevin Bacon 5]

The plugs should be NGK BKR5EKU or BKR5EKUP (platinum).

 

Have you got a pic of the shedded plug? Can tell a lot by looking at it.

[dr_mat 0]

I've heard of blocked injectors causing overheat in single cylinders before ...

[Kevin Bacon 5]

Indeedy.... but I'm thinking his plug is black, so could indicate it being jammed open....althoug replacing the plug has cured the issue, which wouldn't happen if the injector was knackered...it would still run like cack.

 

Plugs are normally shiney and white when they over heat.

 

There should be light grey and dry deposits on them which indicates a healty burn.

[double-6s 0]

mine are black and rather melted.

i will get a pic in the morning and out it up.

BTW, i didn't mention, no.3 was similar but not nearly as bad. by a long way.

[Kevin Bacon 5]

I reckon you've just been giving it the big beans and melted them :-)

[double-6s 0]

you should meet my mechanic kev - he reckons i should be a tester for veedub :)

 

my no.6 was definately like the 'melted' one on that link. but blacker. running so sweetly now. not convinced it'll last though!

[double-6s 0]

durability tester that is ;)

[double-6s 0]

have just fitted some different temp rated plugs - 7 i think, instead of 5.

recommeded by a few people who had the same problems exactly.

seems to be running very nicely now.

we'll see..........

[double-6s 0]

I reckon you've just been giving it the big beans and melted them :-)

 

so can that alone melt them then?? just gunning it?

 

as i do tend to 'av it' all the time really ;)

[Not_Aircooled_or_Taxfree 0]

It may be liquid hot magma :onfire:

[sciroccotune 0]

not really, you would probs need it to go lean for some reason. but it is poss that they fail - crack etc..

[double-6s 0]

sciroccotune, can valve or ring problems make it run lean as such mate?? or is it more likely to be ecu / control in some way??