Replacing the spark plugs is a transitional rite under the gearboxes. It shows that you are aware that your car needs basic maintenance to stay in top shape and that you are ready to tackle it yourself. Congratulations, if you have come this far.
The most common reason to remove spark plugs is to replace them with a new one. However, you might want to first check what form they are in, or you may need to look for sparks to rule out an inflammation problem. Regardless, the process is not as daunting as it sounds, and it is within the reach of an experienced DIYer. After all, a spark plug is just a big bolt that shoots out electricity. Ready? Continue reading for all details.
Why change spark plugs?
How often you need to change your spark plugs depends greatly on the type of car you drive and the type of plugs your engine. Usually the replacement intervals vary between 30,000 and 100,000 miles, but check the manual if you are not sure.
Worn spark plugs can lead to poor gas mileage and a number of performance issues, particularly engine misfires and rough idling and hesitation under acceleration. Eventually your engine will refuse to start if the plugs are too worn out.
Step 1: Find Your Spark Plugs
The first step is to make sure your car actually has spark plugs. An overwhelming majority of them, whether you drive a Toyota Tercel or a Porsche 918 Spyder. However, if your car is powered by diesel, it is not equipped with spark plugs because it has a compression-ignition engine, ie the fuel-air mixture in the combustion chamber ignites without sparking. They have glow plugs, but that's another story.
Once you have confirmed the presence of spark plugs, you must find them. In most modern cars, the spark plugs are near the top of the engine, bolted tightly into the cylinder head. Remember that they might be hidden under a jumble of cables or under a plastic cover. Subaru owners should look for the connectors on the side of their engine, as should owners of Porsche models who are powered by a Flat-Four or a Flat-Six.
You also need to check which spark plugs your engine uses and how many it needs. Normally, the number of spark plugs is equal to the number of cylinders. If you're driving a humble four-banger, you'll need four spark plugs. If you roll around with a V12 under the hood, you will need 12. That is not always the case. Some engines – like a few Mercedes V6s – use two spark plugs per cylinder. Consult your manual or the Internet again.
Found & em 39? Good, let's start. The only tools you'll need are a spark plug bushing for removal and installation, and either a spark plug or a feeler gauge to make sure you have the correct gap. A ratchet is optional, and we strongly recommend that you either buy or rent a torque wrench for assembly.
Step 2: Access to the plugs
When you roll up your sleeves and put your head under the hood, you will quickly notice either a thick wire or a coil that powers each spark plug. Many modern cars use one reel package per cylinder, while older cars typically rely on a single reel for the entire engine. Unscrew the coil pack (or gently pull on the cable) to expose the top of the connector.
Step 3: Remove the old plugs
Using a clean rag or compressed air, remove various foreign objects from the area around each spark plug to ensure that nothing falls into the cylinder when the spark plug is out. Trust us, you do not want that. Once the well is clean, disconnect the plug with the socket. There is a good chance that it takes some fat to get it out. Here a ratchet will make your life easier. Remember: Righty tighty, lefty loosey
Before throwing a three-pointer in the next bin, take a minute to examine the business end of the spark plug; It tells you a lot about what's going on in your engine, especially if you're working on an older car. If the electrode (that is the outermost tip of the connector) is covered with a black substance, your engine will run too fat, which means that the ratio of gasoline to air is too high. If the electrode is coated with a white substance, the engine runs lean and the gasoline-to-air ratio is too low.
Step 4: Gap the new plugs
Use the meter to properly split the new spark plug before installing it. The gap specification refers to the distance between the two electrodes. It varies from car to car, but is usually between .02 and .06 inches. Closing the hole correctly the first time will save you a lot of trouble. Therefore, contact a dealer, your local auto parts store or Google to get the correct measurement if you are not completely sure. Precision is the name of the game here.
Step 5: Install the new plugs
You are ready to install the spark plug once the gap is set. Installation is the reverse of disassembly, but we recommend using a torque wrench to make sure the connector is properly tightened. Tightening should be best left to the professionals, as a plug that is too tight or too loose will inevitably cause expensive, time-consuming damage.
Replace and reinsert the coil (or spark plug cable) Part you had to remove to access the plugs, and you're done. Now just fire the engine to make sure everything is working as planned!