1.2L REVOTRON ENGINE 57 Inspection : The condition of the spark plug provides a good indication of the engine running condition. Knowing what to look for can provide insight to operating conditions and help to pinpoint problems with operation. "Read" the spark plug to determine engine operating condition. 1. Normal - The spark plug core will be lightly coated with grey or brown deposits. Heavy deposits indicate the use of fuel or oil additives. The electrode will not be worn excessively or nicked. The gap will only increase 0.01 mm for every 2000 km of use with the correct fuel. Clean and reuse if replacement is not required. 2. Carbon Fouling - Dark sooty deposits will be present on the entire spark plug. This may cause the electrode to short-circuit, weakening or eliminating spark. Typically caused by excess fuel from a leaking fuel injector, sticking idle speed control valve, or a clogged air filter. Replace the spark plugs if carbon fouled. 3. Oil Fouling- Heavy wet deposits indicate the spark plug is oil fouled. Oil fouling occurs when engine oil is entering the combustion chamber from defective piston rings, valve guides or seals, or a blown head gasket. May also occur during run-in/break In on new or overhauled engines. Replace the spark plugs if oil fouled. 4. Overheating- Overheating is typically caused by the over-advancement of ignition timing, a lean fuel mixture, incorrect spark plug heat range, or incorrect fuel octane rating. Electrodes and insulator will be white and may show signs of wear. Replace overheated spark plugs. 5. Detonation - A detonation or pre-ignition condition will look the similar to an overheating condition, but wear and damage will be much worse such as insulator cracking or breaking. Typically caused by the wrong grade of fuel, incorrect spark plug heat range, or an extremely lean condition. The problem must be identified and repaired immediately otherwise severe engine damage will occur. Do not reuse broken or cracked spark plugs.
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