Visual Check

1. Check the insulator for cracks. Replace the spark plug if crack are present.




2. Check the electrode condition and replace the spark plug if necessary.
If the spark plug electrodes and insulators are fouled with carbon or oil, the engine will not operate efficiently.

There are number of possible causes:
- Fuel mixture is too rich.
- Oil in the combustion chamber.
- The spark plug gap is not set correctly.

If spark plug fouling is excessive, check the fuel and electrical system for possible causes of trouble. If fuel and electrical system are normal, install spark plug of a higher heat range which have the same physical dimensions as the original equipment spark plug.




The following symptoms are characteristics of spark plugs that are running too hot:
- Fuel mixture is too lean.
- Heat range is incorrect.

If vehicle usage does not conform to normal driving conditions, a more suitable spark plug may be substituted.

If fuel and electrical system are normal, in most cases of this sort, the problem can be corrected by using a colder type spark plug with the same physical dimensions as the original equipment spark plug.

3. Check the gaskets for damage and replace if necessary.
4. Measure the spark plug gap.
5. Adjust the spark gap by bending the grounded electrode.