Collision Maintenance Vehicle Care Accessories Performance Motorsports	Symptoms A grayish tan to white color indicates the correct heat range spark plug is in use, the fuel and ignition systems are in good shape, and overall engine mechanical condition is good. Recommendations Replace with spark plugs of the same heat range.     Symptoms Worn or rounded center and/or ground electrodes indicate excessive wear and can cause hard starting, reduced fuel economy and misfire during acceleration. This can also damage other secondary ignition components such as spark plug wires, coils, and the distributor cap. Recommendations Replace with spark plugs of the same heat range and design.     Symptoms Shiny tan or yellow deposits suggest that temperatures have suddenly increased under severe loads. Excessive high temperatures can result in the glazing of the spark plug insulator by allowing fuel and combustion chamber deposits to melt rather than burn off in a normal manner. Recommendations Replace with spark plugs of the correct heat range.     Symptoms Black oily coating can be caused by poor oil control. This usually represents advanced engine wear and results in a complete cylinder misfire condition. Recommendations Check for worn valve guides, valve stem seals and piston rings. In some engines, a defective PCV valve can contribute to this condition.     Symptoms Bent and/or broken electrodes and core nose indicate mechanical damage caused by a foreign object in the combustion chamber or improper reach of spark plugs. Recommendations Remove the foreign object from the engine. Check the Mopar Spark Plugs catalog for proper spark plug application and replace as specified.     Symptoms Chalky white insulator with little or no coloration and extensive electrode wear which is possibly blistered or pitted. The shell may also be discolored from light gray to a dark blue, almost black. Recommendations Verify ignition timing and fuel systems are within specifications and that cooling and emissions are working properly. Check for correct heat range spark plugs.     Symptoms Shiny tan or yellow deposits suggest that temperatures have suddenly increased under severe loads. Excessive high temperatures can result in the glazing of the spark plug insulator by allowing fuel and combustion chamber deposits to melt rather than burn off in a normal manner. Recommendations When the deposits are found on only one side of the spark plug core nose, check the cylinder head (valve stem seals or valve guides). When they are found on both sides of the spark plug, check the piston rings. The spark plug is the correct heat range and was a victim of the engine's condition, not the cause of it.     Symptoms Spark plug shows signs of being hot or blistered, and/or has melted center and ground electrodes. Recommendations Make sure cooling system, spark advance, and fuel mixtures are to specifications. Special attention should be given to the EGR and knock sensor systems. Mis-routing spark plug wires can also lead to cross induction and pre-ignition. Identify cause of pre-ignition and check engine mechanical condition before replacing plugs.     Symptoms Soft, black, sooty, dry-looking deposits indicate a rich air-fuel mixture, weak ignition, or wrong heat range spark plug (too cold). This will result in engine misfire. Recommendations Check for correct plug heat range. On fuel injected engines, check for sticking injectors, malfunctioning cold start valves and/or circuits, and correct fuel pressure. On computer controlled vehicles, the "limp home" computer mode will always result in a rich condition. It is imperative that you check the operation and condition of the onboard computer system. On carbureted vehicles, check choke and choke pulloff, high float level, and needle and seat condition.     Symptoms Small black or gray spots will be noticed on the core nose of the spark plug. In cases of severe detonation, insulators may be cracked and/or chipped. Recommendations Make sure recommended octane fuel is being used. Assure proper operation of cooling, emission, and computer systems with special attention to EGR and knock sensor systems. Identify cause of detonation and repair check engine mechanical condition before replacing plugs.     Symptoms Red to purple deposits on one side of the core nose are an indication of a fuel additive. While many of the deposits are nonconductive and do not contribute to lack of performance, some fuel additives contain octane boosters that leave conductive deposits on the core nose. Recommendations Care should be taken to assure that any fuel additives used are compatible with engine manufacturer's recommendations.