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Plug Conditions Chart

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Spark plug conditions can tell a lot about what is going on inside the combustion chamber of an engine. The chart below shows NGK plugs in various conditions and can help you diagnose engine problems.

A few things to remember when checking your plugs
Plugs should be pulled and checked after the engine has been through a complete warm up cycle by driving. Do not check your plugs after extended periods of engine idleing as this can load up (or foul) the plugs and give a false reading. Be careful when checking the plugs on a hot engine, as they are hot and can remain hot for quite sometime. Most of the time the plugs will not have to be removed from the plug wrench to be checked. Check one plug at a time and replace it in the cylinder it was pulled from. If all the plugs must be removed at once, make sure they are kept in order so they can be placed back in the same locations.

Use this chart below to match your plugs with a engine condition.