Naturally casein-free foods are of vegetable origin. Fruits and vegetables are casein-free foods, and nuts can also be considered in the diet if there are no restrictions. However, some processed foods containing fruits, vegetables, or nuts may not be casein-free foods. Casein is an excellent binding agent and may be used in spreads, dressings, and other processed products.
Engine misfire is the first sign of poor spark. Basically, the spark plugs are firing poorly or incorrectly, so combustion is not ideal or controlled. The sputtering or chugging of the engine is a sure sign of misfire, but a noticeable loss of power or a check engine light due to raised emissions are also symptoms.
Maybe after 5 iterations you would buy a new spark plug. So to fix a misfire, and it looks like a spark plug or plugs are the culprit, you either buy new plugs or run through the procedure above. Just be aware that spark plugs are a consumable. Don't ask me how many miles they last, I've forgotten due to only ever using diesel engines for the last few decades.