Why are there resistors in spark plug caps?

Resistor plugs were developed in the 1960s to suppress some of the spark energy, thus lowering RFI to an acceptable level. Use of non-resistor plugs in vehicles that call for a resistor type can result in rough idling, high-rpm misfire, and abnormal combustion.

How much resistance should a spark plug cap have?

Simply attach or hold a meter probe on each end of the cable and read the total resistance on the meter. The Society of Automotive Engineers suggests the maximum resistance should be 12,000 ohms-per-foot. However, some OEMs have recommended different maximum resistances.

Can bad spark plug wires cause stalling?

If there is any issue with the spark plug wires the engine spark can be disturbed, which can result in engine performance issues such as misfires, a reduction in power and acceleration, as well as a reduction in fuel efficiency. In severe cases bad cables may even result in engine stalling.

What is a spark plug cap?

NGK Spark Plug Caps are designed to reduce “Electro Magnetic Interference” and “Radio Frequency Interference” which can interfere with electronic ignition components causing misfires and poor engine performance. Designed to fit removable terminal nut and solid terminal nut spark plugs.

Can you use a resistor spark plug with a resistor cap?

No idea why both resistor caps and resistor plugs are used together. Both work well with or without resistors. The coils will not be damaged without resistors on the secondary side to the spark plug. The spark plug tip may erode a bit faster.

What is a resistor cap?

NGK Resistor Caps are designed to reduce electro magnetic interference and radio frequency interference which can interfere with electronic ignition components causing misfires and poor engine performance. Resistor covers are for motorcycle, marine, snowmobile and small engine applications only.

Can a bad ignition coil damage a spark plug?

since a faulty ignition coil causes a misfire, it will also cause the related spark plugs to foul. always replace the spark plug or plugs that the bad coil was firing. this will restore the power and fuel economy.