Acceleration rattling noise

Noises can be hard to trace down. If you could take a video of the noise and post it on this site it may help. Beyond that there are a few things to try, First will it make the same rattle if you are setting still and just revving the engine up and down? What about if you put it in gear and hold the brake and rev it? Does it get louder or faster as the rpms change? Does it stop or change if you touch the brake or turn the steering wheel. If you take the van and drive it, and you drive say 30 kph in drive does it rattle, then shift the transmission manually to say second gear, if you go the same speed does the rattle stay the same or does it change. Trying to determine if it's engine or transmission. Next if you listen under the hood do you hear anything like it when it idles? Does it seem to happen under special conditions like you are accelerating uphill or while turning or only going straight? Has there been any work done to the car recently? Have you hit a curb, hard bump or anything like that recently?
Noises can be almost anything, from a loose exhaust shield to an internal engine problem, or from a bad transmission part or even loose trim. That is why hearing it can make a big difference.