Champion Spark Plugs Install - Four Wheeler Magazine

Over-rich fuel condition: This is generally indicated by black and fluffy soot on the insulator. It can indicate a leaking injector or an out-of-adjustment carburetor. This can cause low fuel economy, decreased performance, and even damage to the catalytic converter.

Partially melted center electrode: Can be caused by the ignition being too far advanced, combustion deposits in the combustion chamber, a defective distributor, incorrect air/fuel mixture, or poor-quality fuel. Can result in misfiring, loss of power, and insulator-nose breakage.

Heavy wear on the ground electrode: This can be caused by fuel and oil additives or poor flow conditions in the combustion chamber due to combustion deposits. Because the ground electrode has worn, the gap is far too large and the ignition voltage is no longer sufficient for the large electrode gap. This can cause misfiring and poor starting.

Side electrode bent or moved: The plug contacted either the valve or piston. Using the wrong plug generally causes this. Always use the plug recommended for your vehicle.

Oil-fouled: Oil is entering the combustion chamber. This can manifest itself as either an oil-covered face or by white deposits on the insulator. Causes can be scored cylinder walls, badly worn piston rings, and/or worn valve guides and seals.

Problem: Carbon fouled
Marked by a soft, sooty carbon deposit. If all of the plugs are carbon-fouled, the plugs may be too low of a heat range; the air/fuel mixture may be too rich; the air filter may be dirty; or you may have a weak ignition, a sticking heat-riser valve, faulty choke or bad fuel injectors. If the problem is limited to a couple of plugs in a set, look for sticking valves, a cracked distributor cap, or bad plug wires.
Problem: Carbon fouled Marked by a soft, sooty carbon deposit. If all of the plugs are car
Problem: Thermal Overload
Matt Hallis, Product and Technical Support Manager at Bosch Corporation, says that this can be caused by using a plug that is too hot or by an overly lean air/fuel mixture (like a fuel management, intake manifold, or O2 sensor problem). Surprisingly, Hallis said that another cause can be insufficient spark-plug torque. Since one of the spark plug's duties is to conduct heat away from the combustion chamber, if a plug isn't tight it can't accomplish this goal.
Problem: Thermal Overload Matt Hallis, Product and Technical Support Manager at Bosch Corp
Problem: Carbon flashoverThe folks at Bosch tell us that when this happens, the spark can jump from the electrode to the side of the plug, causing a misfire. One of its causes could be an overly rich fuel mixture or possibly too much fuel pressure.
Problem: Carbon flashoverThe folks at Bosch tell us that when this happens, the spark can