MX-6 L4-1991cc 2.0L DOHC (1993)
Cold plugs have shorter insulators around the center electrode and a larger cross-sectional area for heat to transfer to the cylinder head. Heat is
conducted away from the center electrode quickly and the electrode remains at a cooler operating temperature.
It is important to use spark plugs with the correct heat range for the application. If a spark plug is used with too high a heat range for a particular
application, pre-ignition may occur. Spark plugs with heat range that is too cold for the application will tend to foul easily.
Resistor Type
Most spark plugs are resistor type plugs. These have a carbon resistor built into them to provide radio static suppression and to ensure a higher
sparking voltage. Resistor type spark plugs are always used in vehicles with computerized engine controls because the reduced radio static is less
likely to interfere with operation of sensitive components.
Non-Resistor Type
These are rarely used any more due to their poor compatibility with electronic engine control systems. Also, spark plugs without auxiliary
resistance built in will allow the coil to discharge at much lower voltages (5K-10K volts) resulting in a weaker (lower energy) spark than electronic
ignitions are capable of. These type plugs are used in older breaker point type ignition systems that do not have computer controls and are not
designed to produce the high sparking voltages required by today's emission controlled gasoline engines.