How to Detect Bad Spark Plug Wires

Bad spark plug wires can cause a decrease in engine performance, decrease fuel economy, and can even cause hard starting (a condition where it is difficult to start your vehicle when the engine is "cold"-hasn't run-for more than 12 hours), or stalling. Replacement spark plug wires can be purchased from most auto parts stores. When replacing your wires, you should replace all of them, but you should only work on one spark plug wire at a time to avoid mixing up the wires and changing the firing order.

Things You'll Need

• New spark plug wires

Instructions

1. Turn the voltmeter dial to the "OHMs" setting on the dial, indicated by the omega symbol (Ω).

2. Touch one of the leads on the voltmeter to the metal contact on one end of the spark plug wire.

3. Touch the other lead on the voltmeter to the metal contact on the other end of the spark plug wire.

4. Read the voltmeter display. It should read "0" with a ".05" variance being acceptable. This reading measures the resistance running through the spark plug wires. A low resistance means that electricity is able to travel through the wires without being interrupted. A high resistance indicated a break in the line-the wire is damaged-and the plug wire will need to be replaced.

References

• "How To Repair Your Car: Car-Care Tips, Simple Repairs, Driving & Maintenance Tips, and more..."; Paul Brand, Motorbooks International; 2006
• "Auto Repair For Dummies; Deanna Sclar", IDG Books Worldwide; 1999