VTECVillain

I know that spark plugs tell a good bit about your motor - running rich, lean, etc. What are the signs on the electrodes that distinguish these problems?

YodaIsGod

read this..
NOTE: I know there's more out there about this.....

http://www.ngksparkplugs.com/techinf...s/overview.asp

NORMAL OPERATION appears as brown to grayish-tan deposit with slight electrode wear. This indicates the correct spark plug heat range and mixed periods of high-and low-speed operation. Spark plugs, having this appearance, may be cleaned, regapped, and reinstalled.

CARBON FOULED appears as dry, fluffy black carbon, resulting from slow operating speeds, wrong heat range (too cold), weak ignition (weak coil, worn ignition cables, etc.), faulty automatic choke, sticking manifold control valve, or rich air-fuel mixture. Spark plugs, having this appearance, may be cleaned, regapped, and reinstalled.

OIL FOULED appears as wet, oily deposits with very little electrode wear, resulting from worn rings, scored cylinder, or leaking valve seals. Spark plugs, having this appearance, may be degreased, cleaned, regapped, and reinstalled.

ASH FOULED appears as red, brown, yellow, or white colored deposits which accumulate on the insulator, resulting from poor fuel quality or oil entering the cylinder. Most ash deposits have no adverse effect on the operation of the spark plug as long as they remain in a powdery state. However, under certain conditions these deposits melt and form a shiny glaze on the insulator which, when hot, acts as a good electrical conductor. This allows current to follow the deposit instead ofjumping the gap, thus shorting out the spark plug. Spark plugs, having a powdery condition, may be cleaned, regapped, and replaced. Those having a glazed deposit are to be replaced.

PREIGNITON DAMAGE appears as burned or blistered insulator tips and badly worn

When a spark plug is removed for cleaning or inspection, it should be regapped by the engine manufacturer's specifications. New spark plugs are also to be regapped before installation, as they may have been dropped or mishandled and are not within specifications.


[Modified by YodaIsGod, 5:41 AM 5/31/2002]

Austin

Do a full throttle run, then immediatly shut the engine down, pull the plugs and see how they compare to what the article says...low speed tends to burn some of the deposits off, or add in some black deposits.