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Luis Abarca - Miguel Madrigal, 13 July 2005
Costa Rica , Alajuela

Continues Spark Plug

This message continues with explanations on cause and affect of what you see when viewing you spark plugs.

Ash Deposits
These are light-brownish deposits that are encrusted to the ground and/or center electrode(s). This situation is caused by oil and/or fuel additives. This condition can cause misfires.
The cure for this is to verify worn valve guides or valve seals, not using fuel additives, or you might even try changing fuel brands. By the way, a hotter plug is what most people try to fix this problem. You need to first understand that the plug is NOT typically the problem.
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Oil Fouled:
Oily coating caused by poor oil control. Oil is leaking past worn valve guides, piston rings, or on some race engines a possible intake gasket leak and then entering the combustion chamber.
Check for worn valve guides (NEVER knurl valve guides), intake gasket sealing alignment, as well as worn cylinder walls and piston rings. A leak down test is a good place to start for what is causing this.
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Initial Pre-ignition:
This will usually look as a melted center electrode and/or ground electrode.
Check for incorrect heat range plug, over-advanced timing, lean fuel mixtures, inoperative EGR valve or Knock Sensor (if equipped) and also look for hot spots or deposit accumulation inside the combustion chamber.
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Sustained Pre-ignition:
This will be pretty obvious ... melted and/or missing center and/or ground electrodes as well as a destroyed insulator.
Check for incorrect heat range plug, over-advanced timing, lean fuel mixtures, inoperative EGR valve or Knock Sensor (if equipped) and also look for hot spots or deposit accumulation inside the combustion chamber.
After you see this, you'd better look for possible internal engine damage as well. (pistons, cylinder walls, valves, rings, etc.)
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Splashed Deposits:
These look as if they are small islands of contaminants on the insulator. This is usually a dirty carburetor bores or air intake as well as the possibility of a dirty or faulty injector.
You must use aggressive carb and choke cleaner or other solvent cleaner (a pressurized fuel injection service on fuel injected vehicles or injector removal and cleaning) before installing new spark plugs.
(qt. http://www.centuryperformance.com)

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