Abnormal combustion in methanol fueled engines was investigated using a combination of ion gap detection and pressure versus crankangle measurements. The ability to differentiate between cool flames and surface ignition is shown. It is shown that cool flames do exist in methanol fueled engines. It is additionally shown that they can occur before the spark plug fires producing cycle to cycle variations in the chemistry of the gases present in the spark plug gap. An analysis of the effect of surface temperature, at the time of deposit formation, on deposit induced surface ignition tendency was made.