Spark plug color???

[MyExpWork]

I pulled the 2nd spark plug from the drivers side bank and it was white, what does that mean, if anything? Too lean? And what would cause it?

91 4.0L v-6 163,000 miles.

Oh, and if the plugs are not gapped correctly will that cause knocking?


Thanks,

Brian

 

[Rhett]

What gap are yours? Ford spec is .054".

 

[MyExpWork]

They are gapped within specs from the sticker under the hood. I think it is .046-.054.

Brian

 

[Bashman]

It is indicating an overheated plug. Possible causes are incorrect plug heat range (doubtful since it is the only one), running lean, ignition timing (unadjustble, failed test=PCM change), vacuum leaks or EGR valve (if equipped).

 

[MyExpWork]

What harm could running lean cause? I think its been lean for a while.

Brian