Someone told me that it was a loose rocker arm. They told me how to fix it but due to bad memory can't remember how. So I wonder does anyone know how to fix this? I know they told me that I can't just tighten down the nut that I'd have to take off the rocker arm and manually turn over the motor and figure out when the valve was fully open and then put the rocker arm back on. How would I know when it was fully open?