| 1) The one under the front cover commonly known as the "VTC spring". It's primary function is to preload the internal clearances of the sprocket relative to the cam. It has absolutely no effect on preventing the VTC noise. During VTC operation, these springs do not cycle anywhere near the stress limits of the material and because of this they will never wear out... which is contrary to common belief. 2) Internal spring - this spring is not accessible because the sprockets are built as sealed units, AND it is this spring that allows the VTC to make noise. It's primary function is to hold the VTC piston at the static 0° advance position which is used at idle and high-RPM. Typically, the noise will occur when aftermarket valve springs are used with higher than stock installed pressure. This additional spring pressure pushes against the camshaft on its closing ramps and over-rotates the cam causing the VTC piston to climb its helix and over-power the internal spring. As soon as the cam rotates enough to lower the VS pressure (the valves are closing) the internal spring takes over again and slams the piston back to its stop emitting that audible noise we all love to hate. Now, you asked if there is any risk to not fixing this. Consider that the noise is a result of the cams not being fully controlled at idle. The intake valve's open timing is unchanged, but the closing timing is erratic (somewhere between 0° and 20° advanced) and most likely the idle quality and/or emmissions are suffering because of this. Consider also, that at high RPM the cam's closing event is probably not under control. There might not appear to be any noise, but now there are many other noises at high RPM to compete with. Sure the time is much less between closing events, but there is a possibility that power is suffering because the intake valve's open period is being cut short by an over-rotated cam. Lastly, consider that the VTC mechanism is now cycling out of control for EVERY cylinder's intake valve closing event. At an idle RPM of 700, it is cycling 350 times per minute. The VTC were designed to cycle once every time the RPM changes from idle and once on the rare occasion the engine sees high RPM. This is additional unecessary cycling that adds heat to the oil and eventually it will lead to accelerated wear on the sprocket and the VTC mechanism. It's up to you to decide if a noisy VTC has more drawbacks to it than just simple noise.
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