Hello your hobbyist and fan!!!!!!!!!! Maybe someone can help me, I don’t know any more. Engine: C18NZ 1.8 i with 90 hp Year of construction:91 The engine sounds like it is running on only 3 cylinders in idle mode, but it runs on four, like a trecker sounds like it. Spark plugs are new, air filter is new (sport lufi), idle control is cleaned, ignition cable is checked on a fixed seat. Sometimes the speeds are a bit restless, but the ha t almost adjusted with the cleaning of the idler. Please help me!!!!!!!!! Thank you.