Tighten the spark plug finger-tight until the gasket reaches the cylinder head, then tighten about ½ – ⅔ turn more with a spark plug wrench.
The best way to check spark plug tightness is by inspecting the spark plugs themselves. Try to twist the spark plug. If you can easily turn it around, you have a loose spark plug. If you can't turn it even with a wrench, the plug is too tight.
Overtightening the plugs can cause the shell of the plug to stretch, which will break the gas seals and lead to pre-ignition, or detonation. Furthermore, too much torque can cause the ceramic insulator to become loose in the metal shell and possibly eject from the cylinder head while the engine is running.
If spark plugs are installed below the recommended torque levels, they will not be fully seated in the cylinder head and this will delay the pace of heat dissipation. In most cases of under-torque, the vibrations inside the spark plug cause the ground electrode to break down, causing serious damage to the part.
If your Spark Plugs are failing your engine will sound rough and jittery when running at idle. This can cause vibrations to resonate through the vehicle which could cause further costly damage.
DON'T: TORQUE SPARK PLUGS
Under-torquing is a “don't” because a loose or improperly seated spark plug can overheat which can cause a pre-ignition or a misfire condition. Over-torquing a spark plug is also a “don't” because the insulator can be cracked. As a “do,” I recommend using a short, 200 in.
Does a spark plug need a torque wrench? No, but tighten it snugly, but not too tight, or you won't be able to remove it next time. The most important thing is to start it gently by hand, cross threading it will cause major problems.
While most NGK spark plugs are pre-gapped, there are occasions when the gap requires adjustment. Care must be taken to avoid bending or breaking off the fine-wire electrodes. NGK recommends a round wire-style or pin gauge gap tool to measure the gap.
TOM: Sometimes, spark plugs just work their way out over time. If a plug wasn't tightened properly when it was replaced, it could have just loosened up over time until it finally popped out. If that's what happened, all you need to do is screw it back in.
Lubricate Spark Plugs & Other Parts
For part of your car repair and maintenance, you can use WD-40 to remove carbon residue, and keep moisture away from spark plugs and spark plug wires.
Is Dielectric Grease Necessary for Spark Plugs? Strictly speaking, dielectric grease is not necessary for spark plugs to function; however, as noted above, it is a cheap, easy-to-use material that helps ensure the current moves through the spark plug into the ignition system.
While you can gap spark plugs with household items in some situations, most technicians and car mechanics strongly recommend using a spark plug gapping tool. When gapping spark plugs, your mechanic will use industry-approved tools (a gapper) that do not damage the spark plugs (mainly the center electrode).
Most vehicles will need a 3/8 inch or 1/2 inch torque wrench for working on spark plugs.
You might get a misfire code after spark plug replacement for an individual cylinder like a P0303. The code indicates a misfire in cylinder three. Sometimes the spark plug is dropped, and the ground electrode and the center electrode can make contact. Or the problem could be with the connection to the coil.
From the spark plugs to the ignition coils, many different things can cause an engine to misfire. The most common causes of misfires are worn, improperly installed, and mishandled spark plugs, malfunctioning ignition coils, carbon tracking, faulty spark plug wires and vacuum leaks.
Shaking or vibration may be caused by many different things such as faulty spark plugs, poor fuel pressure or misfires. Other things such as a faulty idle air control valve may cause the engine idle to drop below the normal idling RPM which may also cause the motor to shake or vibrate more than normal.
Misfiring due to excessive heat, quenching, increased fuel consumption and even engine failure can occur from the use of incorrect or mismatched spark plugs, so it's best to replace all of your spark plugs at the same time, and with the correct type of spark plug, to ensure smooth and consistent operation.
A misfire feels like your engine suddenly loses power. You might experience a hesitation when you try to accelerate the vehicle. If it feels like your vehicle is accelerating slower than usual or if it feels rough, the cause could be an engine misfire.
At the top of the list, we have the NGK Spark Plugs. With iridium as its core material, this spark plug pack can operate at a much wider heat range as compared to ordinary spark plugs made out of platinum or copper.