Spark Plug Brown Ceramic

Why would this happen with only 60k on the plugs.

Spark plug brown ceramic. However because spark plugs are changed frequently in racing applications lead fouling has become less common. Every plug i pulled out seems to have burnt ceramic insulators. Its called corona stain. I couldn t focus on the plug.

The rule of thumb is light brown or tan colored deposits on the tip of your spark plugs are normal but deposits of different colors and consistencies can be indications of bigger problems. Spark plug is operating too hot at high speeds. I inspected the spark plugs and applied some of that dielectric grease inside the tube not on the terminals before putting it back in. Lead fouling generally shows up as yellowish brown deposits on the spark plug s insulator nose.

Combustion deposits are slight and not heavy enough to cause any detrimental effect on engine performance. Furthermore indicating the plug is in the correct heat range and has been operating in a healthy engine. It stains brown because of corona spark which is the gap between the insulator and nut and a spark traveling up the plug. Everything is just fine with your spark plug.

Is this why denso replaced these plugs sc20hr11 with the new model sc16hr11. You can reinstall the spark plug. Note the brown to greyish tan color and minimal amount of electrode erosion. Anyway on all of my other plugs the insulators were completely white.

The plugs were also very tight and took a lot of grunt to get them out. Sorry for the crappy cell phone pictures. You sometimes see a very bright white electrode with black dots on it also as a heat range issue in some cases cracked electrodes. Burned ceramic means that combustion gasses are leaking out right.

This condition commonly occurs when gasoline contains too much lead. A normal spark plug will have brown or grayish tan deposits on the side electrode. Replace with a colder heat range of autolite spark plug. Here are the pics.

Normal spark plug color. On this plug it looks burnt all the way around right above the metal case. Appearance ceramic insulator tip appears to have a melted glazed coating. I am thinking they over tightened them and damaged the insulators.

See the hall of shame for one. Good spark plugs will burn fuel efficiently while bad or failing spark plugs can cause the motor not to start at all. Lead fouling can cause your engine to misfire only at high rpm and under hard acceleration. The dealer put the last ones in and they are denso.