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Spark Plug Wire Sets
Questions Answers
When should I replace my spark plug wires? Any time a wire exhibits physical damage either to the wire or the boots, such as a cut, grooves or marks from chafing or scorch marks from burning, the wire should be replaced as preventative maintenance.

Additionally, some wires fail from the inside, due to a breakdown of their insulation materials. Wires should always be inspected and tested whenever a rough or erratic idle is present, poor acceleration is noticed, a decrease in fuel mileage is experienced or a vehicle fails an emissions test due to high hydrocarbon emissions or cylinder misfire fault code.

Wires should be replaced if their resistance exceeds the OEM specification for their specific application. Wires should always be replaced as a set due to the unpredictablility of the internal condition of each individual wire.
What problems can happen if wires do not fit right? Improperly designed wire sets can cause dangerous problems including interference with the throttle cable linkage, causing the gas pedal to stay open, or resting on the exhaust manifold, which would cause the wire to burn. In addition, if wire sets are not installed correctly problems can occur. When installing wire sets, make sure the connection between the spark plug and the cap is secure to avoid ignition problems.
Click here to see damage caused from improper installation of wire sets.Bosch duplicates the outside diameter of the original equipment wire for safe and secure fit in factory retainers and looms. Bosch closely follows the length of the original equipment for safe routing. Bosch always uses snug fitting original equipment style boots and connectors to ensure proper fit, function, and appearance while providing extreme durability and long life. All Bosch boots and connectors meet or exceed the high temperature requirements of the original equipment set.
What are the benefits of using a Bosch MAG core wire set? MAG core wire sets emply a sprial wound, magnetic firing core design. The Bosch MAG core is upgraded to premium by replacing standard metallic wire with a tightly wound low resistance stainless steel wire.

The benefits of the Bosch MAG core includes a hotter, more powerful and longer* spark resulting in optimum engine performance while reducing the chance for misfire and eliminating radio frequency static. There is no better core available.

That's why Original Equipment Manufacturers continue to switch from conventional core construction to MAG core Bosch wire sets for all domestic and Asian cars, trucks, and SUVs are constructed using our premium MAG core technology.
*Laboratory testing has shown 16% longer spark duration over standard suppression construction.
How do you install a spark plug wire set? Click here for instructions
How long do Bosch Spark Plug Wires last? Because we use only premium components, all Bosch Spark Plug Wire Sets are covered by a limited lifetime warranty. A detailed copy of this warranty is included inside every wire set box.
What are some common problems that prevent spark plug wires from working properly?

Spark plug wires are designed to carry the electrical voltage from the ignition system to the spark plug. They are designed to have very low resistance tso the maximum amount of the energy is transferred. This transfer of energy can be interrrupted by several factors:

  • Improper fit – please see questions 2
  • Spark plug problems – If combustion gases leak past the spark plug, the spark plug wires can become unconnected from the spark plug terminal due to the increased pressure. Or, the opposite effect could happen and the gases can cause the spark plug and the wire terminal to corrode and fuse together.
  • Moisture – If moisture becomes trapped in the spark plug hole or between the plug and the wire, it can cause arcing. This will cause permanent damage to the spark plug wires and possibly the spark plug as well.
  • Excessive heat from exhaust headers – Routing spark plug wires in areas with excessive heat can destroy the silicone insulation. To prevent this, all Bosch spark plug wire sets are designed specifically for each application to ensure wires are out of harms way.
  • Loose terminals – Spark plug wires need to be removed carefully. When removing the wire, do not pull on the wire, but instead grasp the plug boot firmly and gently rmove. Make sure the engine is cold. This will pevent the connectors from becoming loose.
What is EMI and do I need to worry about it? Not with Bosch Premium Wire Sets. Electromagnetic interference (EMI), also called radio frequency interference (RFI) is caused whenever a current flows through a wire. This current creates a magnetic field that can disrupt other sensitive electronic components such as the engines electronic control unit or radio. For Japanese and domestic applications, Bosch wire sets have a RFI absorbent shielding material to eliminate interference. In European applications, a solid copper core wire is used with OEM-style resistor connectors that absorb unwanted EMI.