Spark Plug Diagnostics

Because they work on a regular basis, your spark plugs are an excellent indicator to tell you if your car has mechanical or chemical problems that you should address right away. Below are some of the most common symptoms and what they mean. Compare them to a new spark plug and you’ll be able to determine if there’s something wrong with your car.

A worn or eroded plug is one of the most common problems. This simply means that your spark plug needs replacement.

A collapsed plug or one that has the fork caved in is a result of mechanical damage. Get your car checked by a mechanic ASAP because it could be part of a larger problem hiding underneath.

A layer of oil and dust or ash means that a valve or a valve seal is faulty. Get those checked or get them replaced, if necessary.

A carbon-fouled plug means that your spark plugs are operating below the recommended temperature, or that you drive too slowly for too long.

A plug with a layer of fuel all over it could mean that your plug operates at temperatures that are too low, a faulty choke or that the air/fuel mixture that your engine gets has too much of the latter. If the air/mixture fuel that you get is too lean, it results in a white coating on your spark plug.

A red coating indicates that there are additives in the fuel that you use. A spark plug that exploded or that looks like it detonated means that your fuel has too low an octane rating. For either of these two cases, it’s recommended that you change your fuel or get it from another source.