Spark plug operation is essential for normal running of engines thus calling for correct spark plugs to be fitted as recommended for the particular car. If the correct plugs are specified for the engine and the engine is in a healthy state, they should not require attention between their specified replacement intervals and cleaning is seldom required unless facilities are available whereby the electrodes will not be damaged. Ignition coils are fitted in top center of the cylinder head with spark plugs situated below them. To take them off the valve cover and the ignition coils have to be removed at first. Using a spark plug wrench or a deep socket and a little extension bar, unscrew the plugs and make sure that end of the socket does not snap off. Looking at the spark plugs can therefore give the condition of the engine; a light gray color with white matter inside, indicating a lean mixture, or white insulator tip meaning that the plug is too hot while hard black deposits on the plugs mean a rich mixture. Black and shiny plugs justify it and oily plugs may fit an engine with high usage and wear while light tan to grayish-brown proves right mixture and good performance of engine. Multi-ground, platinum or iridium spark plugs are also recommended, they are pre-gapped and it is advisable not to adjust them as it would degauge the plating. Before installing the sleeves, the threaded connectors should be tightened good and the plug surface should be clean, this will reduce cases of cross threading; use a small piece of hose to bring both parts into position. The plugs must then be tightened up to the required torque after which the ignition coils should be replaced.