What you need to know is that spark plugs do NOT last forever.
One thing to keep in mind with respect to performance claims is that no spark plug creates horsepower.
The spark only ignites what is already in the combustion chamber.
If there are any power gains to be had, they will be the result of reduced misfires.
All spark plugs need to be changed sooner or later.
New plugs maintain peak engine performance and efficiency.
Every engine will misfire occasionally.
But as the number of misfires per mile goes up over time, it increases exhaust emissions, wastes gas and reduces power.
All 1996 and newer vehicles have an OBD II onboard diagnostic system that tracks ignition misfires.
When the rate of misfires exceeds a certain limit and causes emissions to increase 50% over baseline levels, it illuminates a warning light.
So on older vehicles, replacing the spark plugs at the recommended service intervals for preventive maintenance will reduce the risk of misfires and maintain peak engine performance.
A new set of plugs is not a cure-all for driveability and emissions problems. In most cases a plug change can make a significant improvement.
New plugs improve cold starting. Bad plugs are often responsible for many cold weather “no start” service calls. Many times the battery has been run dead while cranking the engine because the plugs would not fire. When the old plugs are removed and examined, they are often found to be worn or dirty. Dirty spark plugs can cause fouling which results in misfiring.
New plugs reduce the voltage requirements on the ignition system, which decreases the chance of misfire while leaving more amps for the starter and injectors.
Wet fouled plugs can also prevent an engine from starting, but in many instances the fouling problem has nothing to do with plug wear or neglect.
On fuel injected engines, wet fouling is less of a problem but can happen if a cold start injector leaks or there is a fuel calibration problem that creates an overly rich startup mixture.
New plugs minimize the risk of catalytic converter failure. A single misfiring plug can dump enough raw fuel into the exhaust to overheat and damage the converter.
The presence of higher than normal quantities of unburned gasoline in the exhaust will cause the operating temperature of the converter to soar, which may lead to a partial or complete meltdown of the converter.
This, in turn, may form a partial restriction or complete blockage in the exhaust that creates enormous backpressure and chokes off the engines ability to exhale. The engine may lack power, especially at higher speeds, and deliver terrible fuel economy.
Signs you may need to change spark plugs:
- Engine has a rough idle
- Having trouble starting your car?
- Your engine misfires
- Engine surging
- High fuel consumption
- Lack of acceleration
Replacing spark plugs early makes sense.
The recommendations for spark plug replacement intervals tend to be overly optimistic.
If you’ve already got 80,000 miles on a set of 100,000-mile plugs, they’re 80 percent worn. They are already taking a toll on engine performance and gas mileage. Worse yet, after that many miles, spark plugs have a tendency to seize in the cylinder head.
What If a spark plug breaks ?
Removing a seized plug can be a costly job, especially if the threads in the cylinder head are damaged in the process. When you consider the gas mileage falloff and the possibility of seized plugs, early replacement makes sense.
Here’s the trick on how to punch that porcelain center out without getting porcelain in the cylinder: ( This does not always work but it may save you time and money. )
Turn over the motor and let the cylinder compression do the work for you. If you are lucky you will see the porcelain center POP out of the body. This should leave the metal threads and base of the plug inside the spark plug hole. Depending on the plug and hole size, find the correct easy out and remove the broken piece.
A new set of plugs is not a cure-all for driveability and emissions problems, but in many cases a plug change can make a significant improvement.