Engine Electrical
Spark Plug Wires
Spark plug wires carry high voltage from the ignition coil or distributor to each spark plug. We carry 30 wire sets from $27 to $242 by AC Delco, NGK, TRQ, Bosch, Standard Motor Products and MSD, with strong coverage for Chevrolet Corvette and Silverado 1500 plus Volkswagen Beetle, Mercedes and Porsche models.
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Signs of worn plug wires
Plug wires break down from heat, age and vibration. Common signs include misfires, rough idle, hesitation under load, hard starting and a check engine light with misfire codes. In the dark you may see sparks jumping from a wire to the engine.
Look for cracked or burned insulation, boots that are hard or split, and corrosion on the terminals. Wires that rest on exhaust manifolds often fail first.
Choosing a wire set
Sets are made for a specific engine so each wire has the right length and boot angle. Some include 8 wires and some include 9, since the extra wire runs from the coil to the distributor on some engines.
Core types here include copper, tinned copper and spiral wound stainless steel. Spiral wound wires reduce radio interference. Check whether separators are included, and use the fitment table to match your engine.
Installing plug wires
Replace one wire at a time so you keep the firing order correct. Match each new wire to the length of the old one and route it the same way, using separators and looms to keep wires off hot exhaust parts.
Push each boot until it clicks onto the plug or coil terminal. A thin coat of dielectric grease inside the boots helps them seal and come off easily next time.
Spark Plug Wires questions
How often should spark plug wires be replaced?
There is no single interval, but many owners replace them along with spark plugs on older vehicles or when wires show cracks, burns or hard boots. Follow your maintenance schedule if it lists them.
Can bad spark plug wires cause a misfire?
Yes. A wire with damaged insulation or high resistance can let the spark leak to ground before it reaches the plug, which causes a misfire in that cylinder.
Do I need to replace plug wires with new spark plugs?
Not always. If the wires are in good shape and test within resistance spec, they can stay. Old, cracked or hard wires are worth replacing at the same time.