When the level of the low frequency components is larger than a predetermined value, it is regarded that the noise is generated due to unstable combustion during the low load operation or {HEAD ~ the spike noise} is generated due to {TAIL ~ corona discharge} of a spark plug 16, and the determination of the occurrence of knocking is prevented 
is generated due to
When the level of the low frequency components is larger than a predetermined value , it is regarded that the noise is generated due to unstable combustion during the low load operation or { HEAD ~ the spike noise } is generated due to { TAIL ~ corona discharge } of a spark plug 16 , and the determination of the occurrence of knocking is prevented
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