2005 4.2, while driving to church on Sunday, I felt what could be described as a 'bump' - almost like a bump in the road, but the road was smooth. Immediately, I knew the engine was not running properly, and a few moments later, flashing engine light. Nursed it to church and home, running very rough, shaking badly at idle.
I don't see/hear any vacuum leaks, and the 'bump' and with the small rattle on startup that it has had (plus mileage), and I'm thinking that perhaps a tensioner just went and threw a bit of plastic into the chain, and now one bank is out of whack.
I cross posted this to the 4.2 engine forum, hoping for some other ideas, but if anyone has suggestions on where to start, I'd be very thankful.
Here's a partial scan from VCDS with the tasty bits: