only one black spark plug

[HSV472]

ok about 2 mounts ago i blew the head gasket but befor that my passenger side last plug was always coming out black all fixed now but my spark plug keeps coming out black

its not oil on it its black carbon
what would cause this?

[Vt-Brrrlina]

according to the gregories manual

black plugs can be caused by excessive oil consumption or incorect plug type
also says plugs in this condition are generally not firing

spark plug with burnt electrodes due to incorect plug type loose plug or engine running to hot

cracked plugs from age or using to much force

[HSV472]

ah ok
could a bad /old rotor cap cause this(only one plug)
or a bad injector?

[Vt-Brrrlina]

have fun changin that ive had massive probs with mine as of late and im pretty sure the rotor was the problem - but damn gettn that dizzy cap off......

[vn calais manual]

id be leaning towards be a dodgey injector.

and/or lead.

[greenacc]

could be a leaking valve stem seal on that cylinder , or piston rings perhaps ? Does it burn much oil ?

[HSV472]

doesnt burn any oil at all
also the leads are new and still doing it

[greenfoam]

I had dodgy injectors do this a couple of times. I just throw the injector from the rich cylinder away and put another one in

[Cheap6]

I had dodgy injectors do this a couple of times. I just throw the injector from the rich cylinder away and put another one in

Might be worth swapping the sus. injector with another cylinder and see if the Carbon'ed up 'plug tracks the injector first though.

[savage1987]

if you do need to do the rotor I wrote a how-to on it.. should be able to find it in that section somewhere..


edit: found it
5L EFI - changing the distributor cap and rotor

[krawczuk]

ok about 2 mounts ago i blew the head gasket but befor that my passenger side last plug was always coming out black all fixed now but my spark plug keeps coming out black

its not oil on it its black carbon
what would cause this?

hi, could be low on compression, but my bet is non firing/ intermittent firing plug and or lead .. maybe even coil pack ???
mark k

[PaRaDoX]

flat black is un-burnt fuel ("carbon") check comp, if comps ok then check the dissy cap dissy cap ok swap another injector for this one and see if it still does it

[vn calais manual]

hi, could be low on compression, but my bet is non firing/ intermittent firing plug and or lead .. maybe even coil pack ???
mark k

his car is v8.

[HSV472]

well this week im going to buy new dissy cap rotor button and a new injector

and the comp is perfect
leads ,plugs are new but it was doing it befor i changed them anyway


could it be one of the valves
or
lifters on that cylinder?

[greenfoam]

Unlikely to be anything other than the injector if the compression is normal, I watch my plugs all the time and like I said I've replaced a few over the last couple of years that have gone bad. It may not seem a common problem but I bet it is. Just that no one else cares

[savage1987]

haha jason I don't even know how my compression is I've never had a check on either car.... maybe something i should look into