Reoccuring Misfire!

[logbrog]

My 2001 1.3 yaris sr keeps developing a misfire.

OBD fault code shows misfire in no3 cylinder.

removed spark plug which was damaged around inulator and sooty around ignition coil.

changed the plugs,

350 miles later same misfire,

removed plug again, curved peice over the electrode burnt or broken off.

does it just need new coil or is it anything else.

any help appreciated.

[stantheman1]

This might sound a daft question but are you using the correct plugs? If so were the second set of plugs from the same manufacterer?

[logbrog]

This might sound a daft question but are you using the correct plugs? If so were the second set of plugs from the same manufacterer?

Original denso plugs came out and NGK's went back in.

So Denso in no3 cylinder came out damaged and the NGK in the same cylinder now also damaged.

All other replacement plugs are OK

[gar]

This might sound a daft question but are you using the correct plugs? If so were the second set of plugs from the same manufacterer?

Original denso plugs came out and NGK's went back in.

So Denso in no3 cylinder came out damaged and the NGK in the same cylinder now also damaged.

All other replacement plugs are OK

May be worth getting a compression tester and checking if that's ok! The missing bit may have flown down the bore. I dunno why it would fail on the same pot twice in such a short space of time, without an underlying fault, perhaps timing or valves, piston etc.

Has the car undergone any repairs?

[Raeman]

Hi mate, if it's burned the electrode off the plug, then it's obviously getting too hot in cyl 3.

Not sure why but i would get a replacement set of HT leads, new plugs then try again.

Maybe there's a fault with the HT lead that just supplys cyl 3? so just buy a new lead for that cyl and try that.

Good luck and keep us posted. ;)