Changing a set of spark plugs is a relatively straightforward task on some cars. In other instances, the job can be a nightmare. Some plugs are hard to get to or may have engine components that need to be moved out of the way first.
Spark plugs, themselves, can cost anywhere from $5 to $20, depending on the make and model of your car. Mechanics and auto shops will typically charge anywhere from $115 to $200 for a professional spark plug replacement.
Replacing spark plugs will take roughly an hour if your vehicle has a four-cylinder engine. With a V6 or V8, it could take two to three hours. The cost to replace spark plugs will also vary by vehicle, as some spark plugs designs are more expensive but are designed to last longer.
Don't DIY – You Could Risk Damaging Your Engine
Incorrectly removing or installing spark plugs can cause damage to your engine. Also, care needs to be taken when removing spark plug wires, especially if you plan to reuse them. It's possible to damage the threads inside the engine when installing the spark plug.
Ordinary copper and nickel spark plugs should be changed every 30,000 to 50,000 miles, unless otherwise suggested by the spark plug manufacturer. Platinum and iridium spark plugs tend to last longer than standard copper and nickel spark plugs. Expect to change them every 60,000 to 150,000 miles unless otherwise noted.
Spark Plug Lubrication and Maintenance
WD stands for Water Displacement, so if your spark plugs are wet or you need to drive moisture away from ignition distributors, WD-40 will do the trick. Turn off the vehicle and spray the spark plug wires and the inside and outside of your distributor cap with WD-40.
FACT #4: YOU SHOULD CHANGE SPARK PLUGS EVERY 100K MILES OR SO. So, if good spark plugs are the key to avoiding these issues, how long do spark plugs last, exactly? The general rule of thumb about how often to change spark plugs is that they should be replaced after about 100,000 miles of driving.
If you aren't replacing the wires, make sure you change one spark plug at a time so you can be sure you connect the right plug to the right wire. If you are replacing the wires, look through your vehicle repair guide for a wiring diagram.
Labor Charges
For a faulty spark plug replacement, you can expect to pay anywhere from $40-$350. These charges will also vary from engine to engine. For example, a repair shop may charge $60-$140 for a four cylinder engine.
Fortunately, spark plugs only take about an hour to replace in vehicles with a four-cylinder engine. For V6 engines, the process could take at least an hour longer.
The deposits that build upon the plugs can eventually cause them to misfire. When this happens, the unburned fuel in the cylinders can start to eat away at the cylinder walls. This can cause dangerous pressure levels to build up, and it can even lead to engine failure.
The most common signs of bad spark plugs include start-up trouble, rough idling, sluggish acceleration, declining fuel economy, engine misfiring, and engine knocking.
Generally, it's recommended that you have all the spark plugs (one for every engine cylinder) replaced at the same time. Otherwise, your vehicle might give you inconsistent performance.
Driving With Faulty Spark Plugs
Malfunctioning spark plugs cause engine problems including, misfires, hard starts, reduced gas mileage, rough idling, and lack of acceleration. Driving with a faulty spark plug will be difficult because the engine might fail to function.
Make sure your car's engine is cold before you start. Spark plugs get very hot – only remove the spark plugs when the engine is cool to the touch. It can take a few hours for an engine to cool.
Overheating. Repeated overheating of the spark plug tip can cause the plug to prematurely fail. Overheating can be caused by many things like pre-ignition and a malfunctioning cooling system. Pre-ignition can lead to heat building up in the combustion chamber causing the spark plugs to fail.
Standard copper spark plugs last around 20,000 – 30,000 kms. The spark plugs play an important role in your engine, they produce electrical sparks that ignites the mixture of fuel and air in your engine's combustion chambers, causing the pistons to move up and down.
Dirty or Old Spark Plugs
If your engine is misfiring, you may be able to fix the problem easily by replacing your spark plugs. Spark plugs are relatively easy to remove from engines and inspect for damage, and at less than $25 a piece, they are relatively cheap to replace, too.
Whenever you change spark plugs, it is a good idea to replace the ignition wires and vice versa. This will keep your vehicle running at peak performance and prevent you wasting money on unburned gasoline. In fact, a sudden drop in gas mileage may be an indicator that your ignition system is not functioning properly.
Like all maintenance services, the ideal interval for changing your spark plugs and wires depends on the manufacturer's recommendations. Most cars need them done at 30,000 to 60,000 miles, while others are good until 100,000 miles. The most important thing to remember is to change the wires when you do the spark plugs.
Cars typically do not run worse after changing spark plugs, but there are a few reasons why someone might perceive that the car is running worse: Incorrect spark plugs: If the wrong type of spark plug is used or if the gap between the electrodes is not set correctly, this can cause the engine to misfire or run poorly.