If you own a vehicle with coil packs and spark plug wires and have any of these trouble codes P0300 – Random/Multiple Cylinder Misfire Detected,
P0301 – Cylinder 1 Misfire Detected,
P0302 – Cylinder 2 Misfire Detected,
P0303 – Cylinder 3 Misfire Detected,
P0304 – Cylinder 4 Misfire Detected,
P0305 – Cylinder 5 Misfire Detected,
P0306 – Cylinder 6 Misfire Detected,
P0307 – Cylinder 7 Misfire Detected,
P0308 – Cylinder 8 Misfire Detected,
P0309 – Cylinder 9 Misfire Detected,
P0310 – Cylinder 10 Misfire Detected,
P0311 – Cylinder 11 Misfire Detected,
P0312 – Cylinder 12 Misfire Detected, start your diagnosis with the spark plug wires. Most DIYers assume they have a bad coil pack and THEY MAY. But coil packs usually don’t go bad on their own unless they’re sprayed with water when hot. The best way to fry a coil pack is to continue using your spark plug wires well past their prime. Here’s why.
When the primary field collapses, it induces the magnetic field into the secondary coil with hundreds of turns of copper wire. That can generate up to 50,000 volts to fire the spark plug. If the spark plug wire is in bad shape—high resistance, worn insulation, break in the carbon fiber, the voltage will seek another “path of least resistance” and can arc back to the primary coil or, worse yet, the ignition module. If you’re following me, you’re probably getting the point. If you just replace the coil or module, the new one will fail again. The same thing can happen if the spark plug is damaged. The spark will try to jump to ground at some other location.
You must consider spark plug wires as a wear item and replace them. If you have your maintenance manual recommends spark plug replacement at 100,000 miles, that’s a good time to replace the wires with a new set.
Which wires to buy? A really good set. Don’t skimp on wires. A cheap set has thinner insulation, less robust connections, are the wrong length (usually too long) and with inferior conductive material inside.
© 2012 Rick Muscoplat
Posted on by Rick Muscoplat