Spark plugs are an important component to keep your vehicle running smoothly, so neglecting them altogether or replacing them yourself may not be the best idea. I’ve seen people go to replace their spark plugs and cross-thread a plug. They’ve taken a very common routine repair and turned it into a big deal.
Spark plugs are commonly neglected, but people think, “The car is running, everything’s fine.” They don’t maintain them, and then it costs more to fix later, especially with Ford products. We also see this with Acuras, as well as some Toyotas. The manufacturer often recommends between 90,000 and 105,000 miles for spark plug replacement.
But what we see happen, especially in Ford products, is the spark plug has been in the vehicle so long, exposed to hot and cold and hot and cold, that it has eased itself into the cylinder head threads. You’re not able to remove the spark plug because it has been in there so long. Now the cylinder head has to be removed, the spark plug has to be drilled out, and then the cylinder head reinstalled. You’ve taken typically a $300 or $400 repair and turned it into a $3,000 repair because you didn’t have the spark plugs replaced by a professional.
Another thing we see often when spark plugs aren’t replaced are secondary failures. Spark plugs have what is called a “coil pack” on top of them. A coil pack is designed to send electricity to the spark plug to ignite the air/fuel mixture in the cylinder. Over time, the spark plug wears out. The spark plug gap — the distance between the electrodes of the spark plugs — increases. As that gap gets larger, it takes more and more energy from the ignition coil to fire that spark plug. It’ll get to the point to where the coil will stop working because it’s been overtaxed — in some cases, for several years. It will just stop working.
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Something that would have been a pretty straightforward maintenance repair of spark plugs now requires new spark plugs and four or five ignition coils.
Some cars, like Ford products, will have eight ignition coils if it’s an eight-cylinder, six coils if it’s a six-cylinder and four coils if it’s a four-cylinder. Those can be several hundred dollars to replace. When the coil is damaged, the engine stops firing correctly. Now you’ve got an engine that’s misfiring. A misfiring engine will usually turn on the check engine light, and the check engine light will flash. What that’s telling you is that you are doing damage to your catalytic converter. Most catalytic converters on the low end are $400 or $500. On the high end for some Ford Expeditions, Ford Explorers, Audi and BMWs, you can spend $2,000 or $3,000.
All of this could have been avoided by spending $200 or $300 to replace the spark plugs in a timely fashion.
