Spark Plugs are major parts of your cars and can result to poor performance, lack of power, misfiring, excessive fuel consumption or failure to start the engine. A well tuned engine will rarely need spark plug replacements and will only need regular check up every three months. Improperly tuned cars can cause spark plugs to foul up or deteriorate prematurely. In tuning up engines, except for diesel engines that do not have spark plugs, the spark plugs are the last parts to be checked. It is the same way when troubleshooting for ignition problems. It is frequent that only one or two spark plugs need to be replaced when misfiring is experienced and has been determined to be causing the problem The quickest way to determine which plug is at fault is removing each high tension cable attached while the engine is running. Do it only at one spark plug at a time and inserting the cable back each time before doing the next one. Before doing this exercise, make sure that the cables spark plugs are clean, free from dirt and oil. This is to avoid electrical shock by jumping high voltage current. Although the shock is harmless, it is unpleasant because the voltage shock is somewhere in the vicinity of 30,000 volts! There is no need to do this test if the engine runs very rough, sputters and frequently shuts off. It may well mean several bad spark plugs and cables. Going back to testing each spark plug, once you remove the cable and there is no change in how the engine runs, that will be the culprit spark plug. While when you remove cables from good plugs, the engine will run worse than it is.

Now that the problem has been traced, you can now decide if you only want to replace the bad plug or all. If the plugs are fairly new, it might be okay to replace only the bad one. Let the engine cool down, checking until the spark plugs are no longer that hot to handle. The spark plug remover tool is frequently supplied with the tools of the car because most of the time it has the same use and size as tire wrench. Make sure the removal tool fits snugly down to the base of the spark plug. In loosening the plug, it is best to lightly jerk or tap the remover handle until you feel the spark plug loosen. Stop halfway before completely unscrewing the spark plug. Remove the spark plug remover tool. Blow away the sides of the spark plug thread so no dirt would fall into the combustion chamber. Then proceed to completely unscrew and remove the spark plug. If all spark plugs are to be replaced it advisable to remove and install one spark plug at a time to maintain the correct firing order.

For new spark plugs, usually it is best to make sure you get the correct or recommended spark plugs. If you have the time check with the car dealer, manual or parts shop if a certain heat range is advised for use in engine. High performance engines use cold plugs that have shorter insulators around the center electrode. Lower performance engines use hot plugs with longer insulators around the center electrode. The hot range spark plug burns off deposits around its tips. Check on the spark plug electrode gaps. The recommended gap is often found in the car's manual. The correct gap gauge should slide a little bit tight through the gap without necessarily forcing it. To screw on the new spark plug, lead it in first by a few turns with your hand. Then, fit the spark plug tool and hand tighten it first without the use of a lever or ratchet. From the hand tightened position, tighten it further with use of a lever or ratchet from ¾ to 1 & ¼ turns, no more. That should seat the spark plug washer properly to the base. Before putting on the cable, check if the spark plug tip is screwed on well to the electrode. Also, clean the inside of the cable tips for dirt, oil or corrosion before finally securing it in place. Double check the spark plug terminal connections before concluding it as the last step of a tune up.