I have a jingling sound when i accelerate, it seems to be on the drivers side. You don't hear it when it idles. When you are driving you can tap on the gas, your just even accelerating you hear it. Almost like keys jingling. It is driving me nuts. I do not like strange noises. I have a 99 with a 5.4

 

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Maybe you have a broken shield on cat. Try banging it with your hand and listten for the sound. If you hear it, you can secure the shield by putting a large hose clamp around the cat (this is actually how Ford recommends fixing this).

 

Could also be the backing plate to your front brake rotors. Also exhaust leaks at the manifold can make a sort of metal pinging sound under acceleration, and our trucks are known for exhaust leaks there

 

change getting sucked out of your pockets into the gas tank.

 

Hahahahaha, I wondered wear my change in the coin holders on my console kept going. And to think I thought my wife was taking, .

 

Check your stabilizer bar bushings. Mine wore out and rattled all the time. It's like $20 at autozone and about 15 min to fix. They are located inside the wheel well are are like 6-8 inch bolts with plastic bushings on them. That is, if your busings haven't worn off yet.