Spark Plug Adjust and Replacement

Spark Plug replacemnt and adjustment is infact a maintanence event and not a repair item. Although the maufacturers sometimes recommned a replacement interval as high as 90K miles , it is a good idea to open these and check them at a 3rd of the interal- example every 30K miles. Poor spark plug , produces low engine power and thus decrease the milage siginificantly. The number of spark plug is the same as the no of cylinders , like a 4 cyl will have 4 plugs and a V6 usually has 6 spark plugs.

These come in copper,iridium alloy and platimum electrode tips. Always repalce with similar OEM type.  Sometimes I upgrade to Platimun tips, since these last more and have better performance.

To Prepare :- Get the Correct Plug sockets - see the Tools section,a Torque Wrench, Also have some sand paper handy and a pouch of anti-sieze. The term to be aware of here is the spark plug 'gap' this the gap between the electrode and the ground terminal. The spark plug generates a spark across these points to ignite the fuel mixture inside the cylinder. The intensity of the spark is direcelty ralated to the distance (or gap) between the 2 points and hence the gap is cirtical for prpoer performance.

There is little inexpensive gauge , called the Spark Plug Gauge or Gap Feeler , that can be used to measure and calibrate the gap. You can get this at the Discount parts stores or online. During normal usage the electrode gets worn out and the gap increases, this gap need to be decreased. If the black electrode is worn out or if thee is any kind of dameg on the plugs, you will need a new plugs.

The specified plug gap can be often found on the hood on the inside , usualy on a table. You can also find this information from your User manual / Factory manual So first thing after you remove the plug is clean it a bit by sanding off the carbon inside and around the electrode and ground terminal.

Now using the feeler gauge , check the gap. If the gap is more, take the gauge out , then tap on the ground pin very lightly / Very gently  with small hammer or similar to bring it close to the electode. Reinsert the feeler gauge and adjust it to the correct gap. Apply some antisieze around the threads now, Then carefully seat the plug back in its socket wrench and guide it inside the cylinder walls to reach down and hand tighten it.Finally use the torque wrench to tighten it to the required torque sepcifications. Now mount the coil / plug  wire socket back in the way it was removed.

NOTE :- In some cases the gaps cannot be adjusted and replacement is the only option. So for some performance engines and most european cars , which have a Multi Point Spark Plugs , cleaning and checking gaps is nearly not as easy. It is better to replace them if you find these in a below average condition.