check your serpentine drive belt for fraying.
From what I can tell, the rattle is most likely coming from your alternator, Take It In!
The engine may vibrate causing the front bumper pab=nel to rattle.
If it increases with engine speed, check all of the valve springs and make sure one or more is not broken if not the problem, risk pins or rod bearings are most likely the problem.
it is running to rich, lean it down then it will run
If your rattling noise is coming from behind the dashboard it may be to do with the heater/fan box, replaced a couple. If the noise is coming from the engine bay, then I`d suggest checking oil level first, if it`s a bit low it can take longer to reach the top of the engine on initial start-up, causing it to rattle. Otherwise, take it to a mechanic who you trust...
Diesel engines rattle. They all do.
Valve train clatter.
You need to check all the exhaust pipe hangers, one of them is letting the exhaust rattle against something. Also check muffler heat shield it could also be loose. When transmission in engaged in any gear the engine is torqued to the right, so that is moving the exhaust ( it is attached to the engine so it moves with the engine )into a position to rattle, in neutral the engine is sitting evenly in its mounts so no rattle. May want to check engine and trans mounts too.
tell me the mileage and i will let you know about the rattle
With mine, it tends to be a signal that it is low on oil. Check your fluids and top off any that are low and see if that helps. --------------------------------------------- Check your tensioner and pulley
it will be in one of the valve covers connected to a rubber line. It will be metal and when you shake it, it should rattle.
I had a similar problem with mine. As well the engine would rattle just after stepping on the gas only. I suspected rocker arms. Retorquing them did help with power but did not solve the problem. After tearing things apart, and my truck dying, I discovered the cause of the problem, the connecting rod bearings. 2 bearings where spinning and one was fused to the crank. The slop in these bearings was making all the noise. Interestingly the rattle always sounded like it was coming from the back of the engine or on the passenger side of the engine, not the bottom where I would have expected it to be coming from. I hope that helps.