My Lincoln LS has the AJ30, a Jaguar modified derivative of the Ford 3.0 Duratec. After the engine has warmed up a bit, I begin to hear a rattle under acceleration. Kind of like marbles in a jar being bumped about. It won't happen under heavier acceleration, cruise, or idle, unless it's just too quiet. And I can't hear it when revving the engine while stopped, only when the car is accelerating.

I'm a visual person, I usually fix things by seeing problems and using scan tools and such. Sounds are a lot trickier for me. Anyone have any idea what's going on here? Could it be pinging from bad Oklahoma gas? The car requires 91 octane which I do use. I'm worried it may be a timing chain problem which would hurt because of the time and cost involved to fix that, but I also don't actually know what a bad timing chain sounds like precisely.

Edit: 105k miles, automatic transmission, I think it's the 5R55S