The most common reason for the fuel combustion system to cause carbon build-up on the spark plug is a failed mixture of fuel and oxygen. Overheating Damage: Overheating spark plugs can cause the electrode to wear faster. Proper installation torque is critical in the plug’s ability to dissipate heat out of … Yet 90% of spark plug damage claims are due to improper torque. A visual inspection of your boat engine's sparkplugs can help you diagnose problems. Excessive idling, this causes the engine to run to cold. The plug on the left is fouled with carbon. (Source: Auto Success Online) I looked up the psi and it is supposed to be 70-95 for a 280zx and the mustang is 95-105. Sep 1, 2014 #4 At the top of the link list for fouled plugs is Air/fuel mixture (A/F) too rich. 3. Oil Contamination: If oil seeps onto the spark plug, it will foul the tip. It might help you determine the cause of your fouling. Anything that causes a … It has a fuel cell and a pump from a 98 mustang. 2. There are a couple of things that will cause premature fouling. By Kevin Falvey. Other then that check your distributer cap and also spark plug wires if you keep having spark problems (also depending on your vehicle that type of spark plug wires can cause issues if they're not using tolerances that are equal to OEM). S. SeniorCitizen Lawn Addict. Stuck open thermostat, again this causes the engine to run to cold. Fouled spark plugs can cause engine misfiring, reduced engine power, poorer fuel economy, rough idling, increased emissions, … Pre-ignition from an improperly timed engine can cause this, as can an incorrect air to fuel ratio. If the spark plug is fouling because of a carbon build-up, the reason is likely due to the combustion system of the lawn mower’s engine. This past weekend, I pulled the spark plug from cylinder #4 to check it. I can start and drive it up the street maybe 15 times before they foul out. When I got home, I pulled the plug and found it badly fouled as show in the attached picture. I will list all possible causes from most likely to least likely. Ok I have an 83 280zx turbo and it is fouling plugs like crazy. I went ahead and replaced all the plugs and wires at that time. First thing to do if your spark plug has been fouled is to check the air filter. This rule goes for even the plugs that are pre-measured spacing. In this instance, a case of hard starting was the result of carbon buildup on the plugs. Spark Plug Analysis - Technical Information - NGK Spark Plugs Australia . 1. Joined Aug 28, 2010 Threads 105 Messages 1,805. The most common reasons why your dirt bike has a fouled spark plug are because a dirty air filter, improper pre-mix ratio, carb jetting is too rich, the engine has low compression, or a weak spark. Tips For Fouled Spark Plugs. If this occurs a number of times after the spark plugs have been replaced, the engine is flooding with gasoline. 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