Q: When should I use a resistor spark plug?
A: NGK "R" or resistor spark plugs use a 5k ohm ceramic
resistor in the spark plug to suppress ignition noise generated during sparking.
NGK strongly recommends using resistor spark plugs in any vehicle that uses on-board
computer systems to monitor or control engine performance. This is because
resistor spark plugs reduce electromagnetic interference with on-board electronics.
They are also recommended on any vehicle that has other on-board
electronic systems such as engine-management computers, two-way radios,
GPS systems, depth finders or whenever recommended by the manufacturer.
In fact, using a non-resistor plug in certain applications can actually
cause the engine to suffer undesirable side effects such as an erratic idle,
high-rpm misfire, engine run-on, power drop off at certain rpm levels and
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