- The Washington Times - Friday, August 17, 2001

Like everything else on your late-model car or truck, spark plugs are infinitely better than those of years ago. Among the changes you'll see in today's spark plug is the use of rare, precious metals on the electrodes. Some plugs use titanium for longer-than-normal life. Others use iridium.

These changes have increased the price of the typical spark plug, but they've also extended its useful life. It's not uncommon for a set of spark plugs to last 50,000 or even 100,000 miles. However, it's good practice to inspect your engine's plugs once a year or about every 15,000 miles. Even if the plugs are still working fine, they can give you an excellent glimpse into the rest of the engine.

Check the spark plugs only on an engine that is fully cool to the touch. In order to inspect a spark plug, first disconnect the heavy wire that conducts electricity to it, or if your engine is equipped with an ignition coil for each spark plug, remove the coil. Don't ever just grip the wire and twist and/or yank on it to get it off the plug. You may damage the core of the wire, rendering it useless. Instead, use an inexpensive spark plug boot puller or spark plug wire-removal tool. These come in various styles at the same auto-parts store that sells spark plugs. Getting an individual ignition coil off usually involves undoing a couple of clips or retaining screws and lifting off the coil.

To avoid confusion and problems later, remove only one spark plug wire at a time. If you're faced with a tangle of spark plug wires when the time comes to reconnect them, you may not know which wire goes to which plug. With the spark plug exposed, blow some compressed air, or blow through a drinking straw, to get any debris away from the base of the spark plug.

To remove the spark plug, you'll need the correct size spark plug socket, attached to a ratchet via an extension. If you're not sure what size socket you need, check the owner's manual, the under-hood tuneup decal, or consult with the professional who sells auto parts.

With the socket firmly seated on the steel hex of the spark plug, turn the ratchet counterclockwise and the plug should thread out. As you remove each spark plug, check the end that was in the engine. There you'll find its electrodes. The center electrode is a metal post surrounded by porcelain. The side electrode is a bent piece of metal connected to the threaded portion of the plug. The gap between them must be a specific size as dictated by the carmaker. Also carefully inspect the porcelain insulator which is the part of the spark plug that's outside the engine. Look for cracks or chips or damage to the porcelain. If you find any damage, replace the plug.

The electrodes should have a light coating of golden brown. If the plug is sooty, caked with carbon, blistered white or otherwise looks suspect, have the engine checked by a qualified professional. If all is well, check the size of the gap with a special spark plug gap gauge. If the gap needs to be adjusted, bend slightly and carefully — the side electrode. Do not try to file the center electrode.


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