Spark Knock noise?

Originally Posted by TedB370z

...But now, at low RPM, only when in gear, I get valve chatter, the spark knock was masking it, as its a similar sound but now the spark knock/dieseling gone, you can more clearly hear it I've read this could be anything from crappy oil or need to run synthetic (I've only ever run 5w30 conventional oil by Castrol, Valvoline or Quaker State, even in my 350z) ...