Checking your spark plugs is one of those essential winter car maintenance jobs for anyone with a gasoline-fueled vehicle. With plunging temperatures, getting your car engine can be harder to do, so making sure you have a fully functioning set of spark plugs can make all the difference—and save you money.
Our experts put together a series of guides for you on the proper car maintenance you can do to get your car ready for harsh weather conditions. Below you can find out all about spark plugs: the benefits of changing them, how to know when you need to change them, and how to replace them yourself.
The Importance of Replacing Your Spark Plugs
Spark plugs, which generate the spark needed to ignite your car’s internal combustion engine, become worn and need to be replaced over time. By replacing your spark plugs, you’ll avoid any engine damage from driving with worn spark plugs, which require more voltage to fire and place strain on the battery. Taking a few moments to prepare your car for extreme weather conditions can keep your vehicle on the road longer and reduce the chance of a sudden auto repair.
Generally speaking, spark plugs need to be checked and changed every 30,000 miles. Consult your owner’s manual or your local mechanic to check if there are any special requirements for your vehicle.
If you’re unsure on whether or not your spark plugs need replacing, look for the following symptoms when driving:
- Low fuel economy
- Difficulty starting the engine
- Engine misfiring and surging
- Juddering sounds when idle
- More exhaust fumes
Choosing the Right Spark Plugs
There are two main types of spark plugs: hot and cold. High-performance cars use cold plugs to generate more heat in the combustion process and help transfer it away quickly. More common vehicles use hot plugs.
Spark plugs also differ in quality, depending on the durability of the material used in the electrodes. Copper spark plugs are more affordable, but if you want your plugs to last longer, you’ll want to upgrade to platinum or iridium spark plugs. The latter can last much longer than copper ones. You can also get double-platinum ones, which some cars require.
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Before buying your replacement spark plugs, check your car owner’s manual for any specific instructions from the manufacturer.
How to Check and Change Your Spark Plugs
Changing your spark plugs is a straightforward job you can do yourself. If in doubt, or you don’t want to do it yourself, a trusted mechanic can assist in getting this done.
What you’ll need
- New spark plugs
- Spark plug socket (and extender if required)
- Torque wrench
- Spark plug gap tool
- Can of compressed air
- Clean rag
Check your spark plugs
Make sure the engine is cool before you start your spark plugs checked.
First, check the vehicle handbook to see how you can access the spark plugs. This differs from vehicle to vehicle. Most have one plug per cylinder, and the plugs will fire in a particular order. Check how many sparks plugs your car has and follow step one below to remove and inspect them to see if they need a change.
You’ll want to change them if you’ve had them for over 30,000 miles if you’re experiencing the above performance problems, if you’ve got a check engine light showing, or if you notice any of the following things on a visual inspection of the plugs:
- If the spark plug is dirty or shows signs of melting or heat blistering.
- If the end of the spark plug has rusted, this can cause a poor connection.
- If the spark plug is covered in oil or soot. Note that a reddish-brown coating on the plug’s ceramic part is typical and not usually a sign of any problems.
- If the spark plug has cracks, chips, or other damage.
- If either of the electrodes appears eroded or have an excessive buildup of deposits.
- If the electrode gap is too wide, which you can check by comparing it with a new plug or by using a spark plug gap tool.
If one of your plugs needs to be replaced, we recommend replacing the whole set simultaneously.
Changing your spark plugs
Change one at a time following the procedure below.
Step 1: Remove the old spark plug
Remove any debris from around the area with some compressed air and a rag.
Carefully remove the wire by pulling the boot (not the wire itself). You might need to use pliers for this.
Use the compressed air again to remove any dirt that could fall in the gap when you remove the spark plug.
Use the spark plug socket (and an extender if needed) to unscrew and remove the plug.
Step 2: Prep the new spark plug
Before you insert the new spark plug, compare it to the old one. They should be the same size and the different parts should match up. This is a quick, useful check to make sure you’re using the right plugs.
Next, make sure the new plug is gapped correctly. You can check your car’s requirements in the owner’s manual, and it may also be displayed in the hood of the car. Use the gap tool to check the gap between the electrodes of your new spark plug and, if needed, to adjust the gap a tiny bit at a time.
Apply grease to the ceramic part of the new spark plug. Not all spark plugs need lubricant on the thread, so double-check with the spark plug manufacturer first if it isn’t mentioned on the box or in the instructions.
Step 3: Insert and tighten the new spark plug
Place the new plug into the spark plug socket and insert it, screwing it in by hand.
Use a torque wrench to tighten it, but not too much as you don’t want to damage the thread.
Replace the spark plug wire by pushing the boot back in on top of the spark plug until you hear it click into place.
Now repeat these three steps with the other spark plugs. Then you’re done!
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