last night at 135mph my focus rs started to stutter. after that i was taking it easy but when cuming on boost the car would holdback and misfire so today i checked my plugs. all plugs were fine but cylinder no.3 please see pics!!!!!!!!!!!!! whats doin this? just been mapped 320hp @ 17psi. these plugs were an uprated part that were fitted to cope with the extra power. can any1 help?

 

its must be running lean at that sorta load level.

 

would this be evident in only 1 cylinder?

 

yeah quite possibly,, due to manifold designs ETC. , or injectors not being completely identical ETC.

few reasons it would of done it on only one cylinder first... Cossies seem to do it on number 4 first IIRC.. but no idea about FRS

 

They should have checked the flow of the injectors first to make sure they are a balanced set.
The design of the inlet will cause a slight difference in fuelling, but not normally enough to matter, the main thing though that causes the difference is the WATER PUMP, or rather it's location relative to the cylinders, the nearest one receiving the best cooling, on to the furthest one getting hotter than the others as water has heated on the way through past the other cylinders.
I always check the injectors if there is one slightly higher I put that in no4, slightly lower will go no1 etc.
It does look v white, but may just be running very clean, hard to tell from piccie, I think just replace and you'll be ok, but I would get a full load fuelling check done asap.
What plugs are they by the way ?, a HG on the way out can do some odd things, had that before melted the earth electrode, but also turned the plug green!!
tabetha

 

they are ngk's ptr5a 10
all other plugs are fine bar no.3 which if definatly not gone white same normal colour as other's. the electrode is completly burnt out as well as obvious top part missing!

thanks for info shall be taking it back nxt week to be sorted out. its been fine apart from when the cars quite cold when u full throttle it it stutters and backfire's befor goin and when goin full chat at 135 and 1 giving up! and they only done 1000miles!

 

is it ok now you have put new plugs in? as there is a chance of valve damage after
things like this.

 

i went halfords earlier and got o.e plugs so i can only run 270hp. luckily i have switchable maps. cant run performance map on these plugs but so far car is fine no probs. will send it back to tuner to put betta plugs in an another blast on the rollers.

hopefully no damage to the cylinder/piston or valve. if it does have damage that means i will have to kill the tuner!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

watch this space. cheers

 

As tab says water pump location has a lot to do with engine overheating the back cylinders , and as no 3 has 2 cylinders next to it , seeems always to be the first to go , cosworths melted no 3 pistons first , for the same reason , no 4 even though is further away has only one cylinder heating the water chackets around it .