Spark plugs are an important part of gasoline-powered car engines. Without them, the engine won’t start, and if they’re raw, the engine will run poorly. Almost all Gasoline-powered cars are equipped spark plug, regardless of whether you drive or not a new Porsche 911 or the 1990s Toyota Corolla station wagon. Most engines use one plug per cylinder, so V6s typically have six plugs, but some cars require two per cylinder.
How often you need to replace spark plugs depends on many factors such as the type of car you drive, the way you drive, and the distance traveled. Signs of a bad spark plug include a hard-to-start engine, incorrect ignition, or idling. While it may seem daunting to tackle this task on your own, it’s a lot easier than you might imagine: A spark plug is a spark that fires electricity. Roll up your sleeves and get started.
What you need
- New spark plugs
- Spark plug wrench
- Distance meter or sensoriometer
- Wrench (optional)
- Tape (optional)
1. Locate the spark plugs
First, you need to find your spark plugs. They are bolted to the cylinder head, near or at the top of the engine, but they can be hidden under a plastic cap that you have to pop off. On older cars you can find them by following the lead from the distributor – one comes from the coil but the others go straight to the plug. On many newer vehicles without a distributor, each plug has a coil of wire that needs to be removed.
We are using a 1972 Mini project car to illustrate the process. In the photo below, the spark plugs are below the top end of each blue wire. This guide is not specific to specific Mini programs and it also applies to motorcycle, lawn mowers, and chainsaws, among others.
2. Remove the old plugs
Removing the spark plug is simple because it’s basically a bolt. Straightforward, loose, righteous. Start by removing the wire or coil of the spark plug. Removing the rope is simple: Gently pull on the rope and it will come out. Do not touch the ends of the wires leading to the distributor (unless you need to get more space) and we recommend labeling each wire using duct tape so you get them back in order. If you are dealing with coils, they can be secured with a bolt that varies in size depending on the model. Either way, you’ll soon see the plugs. Before you take them out, remove any debris that has built up in the spark plugs; it may fall on the motor if you don’t.
When the plugs are accessible and the wells are clean, it’s time to turn the spark plug out. There are several styles: Some mechanics prefer to use sockets that they can attach to the ratchet, while others prefer to work with specialized wrenches. It doesn’t matter what you use as long as it’s the right size and it fits the plug. Remember that using a regular socket can damage the spark plug.
3. New spark plug gap
Some spark plugs are pre-installed while others do not need to be opened. If you fall into either of those categories, you can skip this step, though it’s a good idea to check that the space on the front throttle unit is properly set. If either box is not checked, you will need to use the clearance tool (or feeler gauge) to adjust the gap between the ground and the center electrode. It varies from car to car, though it’s typically between 0.02 and 0.06 inches. “Close enough” doesn’t cut it here, the motor will run poorly or won’t run at all if the clearance isn’t set properly, so check online or in the service manual if necessary. Also, the gap is usually clearly marked on your new spark plug cartridge.
Let’s say we are working with 0.04 spacing. If the gauge does not match between the electrodes, the gap is too tight; Gently bend the ground electrode outward to extend it. If the meter fits but does not touch either electrode, the gap is too wide; Gently bend the ground electrode in to tighten.
4. Install new spark plugs
Install the new spark plugs in the reverse order of when you took them out. Start by tightening them gently (by hand if possible) and use a wrench to secure them about one-eighth of a turn through tight by hand. Better yet, use a torque wrench and find the specs in your car’s service manual or by searching online. Never tighten spark plugs; you can cause disabling (and extremely costly) damage to your engine.
Turn the cord or coil back to the plug, start the engine to make sure it’s running properly, and you’re good to go.
What should I do with my old spark plugs?
Whatever you want: Toss them in the nearest trash can, keep them as souvenirs, or weld them into sticks. Regardless, always consider the electrodes before you dispose of them, as they can tell you a lot about the shape of your motor. Dry black matter could mean the engine is running too rich – it’s getting too much gasoline. If you see a heavier, wet, black substance, it’s likely engine oil is entering the combustion chamber (you can also see blue smoke coming out of the exhaust). If they are coated with a white substance, the engine may be running too thin.
