spark plug color

[demonZ73]

ok so i got my car to idle while it was idleing i pulled coild plug number one and idle dropped so i did coil pack 2 and 4 and did not notice a drop.........sure enough i pulled the plug in cylender 1 and had a nice gray (clean) look to it, however when i pulled 2 and four they are BLACK does this indicate bad ignition coil and the plugs are just fouling?.........thank you for reading and your help

[demonZ73]

ok i just put coil pack 4 in cylinder one and unplugged it engine died down now i KNOW i have a few bad ignition coils

[t.mcginley.jr]

yeah make sure to replace all bad coil packs

for the spark plug color, this is from TT.net:

The following is from the NGK homepage:

Reading spark plugs can be a valuable tuning aid. By examining the Insulator firing nose color, an experienced engine tuner can determine much about the engine's overall operating condition.

In general, a light tan/gray color tells you that the spark plug is at the optimum temperature and that the engine is in good operating condition.

Dark coloring, such as heavy black wet or dry deposits usually indicate a fouling problem. Heavy, dry deposits can indicate an overly rich condition, too cold a heat range spark plug, possible vacuum leak, low compression, overly retarded timing, or too large a plug gap.

If the deposits are wet, it can be an indication of a breached head gasket, oil control from rings or valvetrain problems, or an extremely rich condition, depending on what liquid is present at the firing tip.

One must also look for signs of detonation, such as silver specs, black specs, or melting or breakage at the firing tip.

Signs of fouling or excessive heat must be traced quickly to prevent further deterioration of performance and to prevent possible engine damage.