Know the condition of the engine from the spark plugs
1- Good condition
2- Saturated with oil due to a problem in the piston
3- Needs to adjust the (gap) in the new spark plug
4- Evidence that the spark plugs have not been changed for long periods and needs to be changed immediately
5- Saturated with lead due to a high percentage of lead in the fuel
6- Saturated with carbon due to poor combustion, the fuel pump and air filter need to be checked
7- As a result of the engine temperature increasing above its normal rate, and therefore we check the system
8- Needs to change the type of fuel (for example, instead of 80 gasoline, it is 90 or 92 gasoline) or change the valves if it happened in a short period (less kilometers)
9- Evidence of a mechanical problem or a foreign body in the combustion chamber
