What a VVT sprocket does
Unlike a fixed sprocket, a VVT sprocket contains an internal mechanism that allows the camshaft's position to be adjusted relative to the crankshaft while the engine is running, optimising performance, economy and emissions at different engine speeds. It's a precision component, and the internal mechanism can develop play as it wears.
Common symptoms
- A rattle that sounds similar to timing chain wear, sometimes more pronounced at idle
- Timing correlation fault codes, similar to those caused by chain slack
- Rough idle or hesitation as valve timing drifts from its intended position
Why the distinction matters
Because a worn VVT sprocket and a worn timing chain tensioner can produce very similar symptoms and fault codes, it's easy for the wrong part to get replaced if the diagnosis isn't thorough. We check the whole timing system — chain, tensioner, guides and sprockets — rather than assuming, so you're not paying to fix a chain that was never the problem.