My girlfriend owns a 2008 Mazda 2 (110k) and recently developed knocking sound when the engine is cold. In my small amount of experience, it sounded like bearing or piston slop. Upon further thought and testing I actually found it to be the VTCS butterflies. I found this by removing the plug to the control motor and the issue went away. Also, the issue only existed with the blue "cold engine" light on, as soon as it turned off the noise disappeared.

My question is: Should I take the manifold off and inspect the flaps, or is it just the bushings on the control rod that are rattling and not a big deal. I've seen that some engines have screw on flaps and some are slip on. As i do not know which on the mazda 2 has, i would hate for it to be a screw on flap and have it come off in the engine!

Many thanks for any help or information :)