Got this rattle in my saab's timing chain. Figured out it was caused by an upper timing chain guide. The plastic becomes brittle with time, and when the chain "smacks" up against it, it makes a sound.
In my case, I was lucky. The plastic has 3 points where it's clipped in. 2 of these points had brokes of on mine.
Hope this video comes in handy for some other People out there with saab's.
Part number for this item was: 90537337. There are more partnumbers for this that is interchangeable.
