Detonation? posted by Cherry3z on January 31, 2014 at 09:20 AM
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I've never seen a Z detonate without load, so I think you'd have to be trying pretty hard to get it to knock by revving in neutral. I agree that it sounds like a failed idler bearing or something along those lines. See if you can narrow it down to a general area on the engine (front upper, front lower right, etc) and that might help guide you towards what's failed. I'd suspect either a bad timing belt idler (especially if it hasn't been done before) like everyone else is saying, but it could be elsewhere, too.
