Diagnostic Tips

Checking Spark Plug Wires

Worn or damaged spark plug wires can cause engine misfire that could result in engine starting difficulty, rough idle, lack of acceleration, engine bucking, lower fuel mileage and excessive emissions. Shown below are some techniques to determine whether it is necessary to replace the spark plug wires:

Visual Inspection (Engine On)

Look at the wires and listen for any sign of:

Arcing
Make sure there is no intermittent spark occurring anywhere along the exterior of the spark plug wires. This is typically seen as a short blue spark and heard as a cracking or snapping noise. Pay particular attention to points along the spark plug wire that are close to ground planes or other wiring.

Visual Inspection (Engine Off)

Look at the wires and listen for any sign of:

Soiling
Make sure the wire, boots, and nipples are not caked with oil, grease and dirt.

Damage
Make sure the wire, boots, and nipples have no burns, cracks, chafing, or obvious signs of damage such as cuts, swelling, etc. Visually compare to each other to note potential damage.

Electrical Tracking
Make sure the boots, spark plugs, performance ignition wires, nipples, and wire to coil/distributor tower show no signs of tracking. Tracking is most commonly seen as a thin erratic burn line on:

The outside surface of the spark plug and/or coil/distributor tower.
The inside surface of the boot and/or nipple; or the outside surface of the wire at the end of the boot and/or nipple.
(If tracking is observed on the spark plug, coil/distributor tower or inside surface of the boot and/or nipple, the spark plug wire and the mating part must be replaced.)

Arcing to Grounds
Make sure the spark plug wires are not arcing to any ground plane such as an exhaust manifold, engine bracket, heater hose, etc. Spark plug wires should not be in contact or within 1/2" of any ground plane.

Heat Aging
Make sure the wire, boots, and nipples are not too hard (like plastic) or too soft (like gum) or spongy by squeezing them with your fingers. These rubber components should feel firm, like a pencil eraser.

Open Circuit / Heat Resistance
Make sure the spark plug wire does not have an open circuit, and as a general rule, the resistance should not exceed 1,000 ohms per inch (but may be permissible by some O.E. manufacturers' specifications). To check, perform the following steps:

Remove the spark plug wire from the engine.
Using an ohmmeter, measure the resistance of the spark plug wire from terminal end to terminal end. If no reading is observed, the spark plug wire has an open circuit.
Measure the length of the spark plug wire in inches. Divide the resistance reading by the length of the spark plug wire to determine ohms per inch.

If any of the conditions noted above exist, replace the spark plug wire and follow the installation instructions located inside your new ProConnect™ Spark Plug Wire Set.