Engine Knocking - Causes of Pre-ignition

Causes of Pre-ignition

Causes of pre-ignition include the following:

• Carbon deposits form a heat barrier and can be a contributing factor to pre-ignition. Other causes include: An overheated spark plug (too hot a heat range for the application). Glowing carbon deposits on a hot exhaust valve (which may mean the valve is running too hot because of poor seating, a weak valve spring or insufficient valve lash).
• A sharp edge in the combustion chamber or on top of a piston (rounding sharp edges with a grinder can eliminate this cause).
• Sharp edges on valves that were reground improperly (not enough margin left on the edges).
• A lean fuel mixture.
• An engine that is running hotter than normal due to a cooling system problem (low coolant level, slipping fan clutch, inoperative electric cooling fan or other cooling system problem).
• Auto-ignition of engine oil droplets.
• Not Putting Oil In The Engine