Here are various pictures of spark plugs and some problems that can be identified by the appearance of the spark plug:
Images 1 & 2: This is a mixture of gasoline is too poor, the insulator tip is gray and white, but can also be yellow-gray.
Images 3 & 4: Like velvet, dull black carbon deposits on the electrode insulator, and the shell is caused by one of the following: a mixture of wrong, dirty air filter, automatic choke is broken, the spark plug is too cold, or how the stop and go driving is extrem . To fix this, re-setting air and fuel mixture, replace the air filter or use hot plugs and fix how to drive
Images 5 & 6: Wet, caused by: excess oil fill, cylinder wear, piston rings or valves. To fix this problem, repair and / or replace worn parts. In any case, the spark plug should be replaced.
Images 7 & 8: Deposit on yellow isolator is from fuel additives containing lead, the deposit will be conductive and cause knocking. Spark plugs need to be replaced because these deposits can not be cleaned
Images 9 & 10: Deposit with brown and yellow color is a combination of carbon and lead from fuel and oil additives. They accumulate in the insulator during slow driving conditions and, at high speeds they melt. This deposit will harden when the spark plugs in cold conditions and melt when the spark plug in the hot conditions. Once again, cleaning and sandblasting are useless; Must replace new spark plugs.
Images 11 & 12: Brownish like charcoal on the electrodes and insulators are the result of carbon buildup in the combustion chamber and to improve it in some cases have to carbon clean machine, before installing a new spark plug
Image 13: Electrode melting caused by excessive heat and as a result of the selection of the type of spark plugs
Image 14: The middle of the electrode melts, as a result of abnormal combustion: eg knocking or timing set too high
Image 15: Electrode melting caused by the ignition is too low or too high, the air and fuel mixture is too poor or piles of carbon deposits in the combustion chamber is too thick ..
Image 16: Electrode thinned a bit because it was too long not replace spark plugs
