Your car's spark plugs become weaker over time, leading to performance problems such as stumbling, surging, or loss of power. If you allow the spark plugs to wear out completely, your car will not start. Depending on the model of car and how you drive, spark plugs may last as long as 60,000 or may need to be changed after just 10,000 miles.
Lots of things can cause spark plugs to go bad prematurely. If your car's air-fuel mixture is too high the spark plug tip can burn up, or be coated with residue that makes the spark weaker. If the fuel mixture is too low, it can lead to fouling of the tip with gas. Other mechanical problems can cause the spark plug's tip to be fouled with oil.
Fuel additives can leave reddish deposits on the spark plug nose. When you remove the spark plugs, examine the tip of each one. A normal used spark plug will have a grayish or white tip, and every part of it will be intact. If any part of the spark is missing or has any other color or type of discoloration, talk to your mechanic.
To get started on this simple do-it-yourself car maintenance task, gather your tools and supplies:
- new spark plugs for your model of car (ask at the auto parts store or search for your specific make and model if purchasing online)
- socket wrench handle
- 17mm deep socket to loosen and tighten the plugs
- a socket extender if your plugs are located far down in the engine
- a magnetic wand to reach down into the cylinder to remove the spark plug
1. Disconnect the negative battery terminal before you begin working under the hood. If you do not disconnect the battery a spark can start a fire, a misplaced move with the wrench can short out fuse, or you can even be electrocuted. If you're not sure how to do this step, you may want to let a qualified professional change your spark plugs for you.
2. Locate the spark plugs on the cylinder head. Unhook the fuel injector wires above each cylinder.
3. Pull out the insulator. Use your socket wrench to loosen each plug. Do each spark plug one at a time. Remove the old spark plug.
4. Insert the new spark plug in the tip of the insulator. Place the new plug in the cylinder, and turn it a couple of times with the insulator.
5. Remove insulator and finish tightening with your socket wrench. Replace insulator, hook injector back wire up.
6. When all four plugs are installed, inspect everything one more time for loose connections or tools left behind.
7. Reconnect the negative battery terminal. Start the car; if it starts and runs, you're done!
Wright, M. How to Replace Your Spark Plugs. Accessed September 25th, 2012.